Allotropes Allotropes are different forms of the same element. Different bonding arrangements between atoms result in different structures with different chemical and physical properties. Allotropes occur only with certain elements, in Groups 13 through 16 in the Periodic Table. This distribution of allotropic elements is illustrated in Figure 1.

Group 13

Boron (B), the second hardest element, is the only allotropic element in Group 13. It is second only to carbon (C) in its ability to form element bonded networks. Thus, in addition to amorphous boron, several different allotropes of boron are known, of which three are well characterized. These are red crystalline α -rhombohedral boron, black crystalline β -rhombohedral boron (the most thermodynamically stable allotrope), and black crystalline β -tetragonal boron. All are polymeric and are based on various modes of condensation of the B 12 icosahedron (Figure 2).

Group 14

In Group 14, only carbon and tin exist as allotropes under normal conditions. For most of recorded history, the only known allotropes of carbon were diamond and graphite. Both are polymeric solids. Diamond forms hard, clear, colorless crystals, and was the first element to have its structure determined by x-ray diffraction. It has the highest melting point and is the hardest of the naturally occurring solids. Graphite, the most thermodynamically stable form of carbon, is a dark gray, waxy solid, used extensively as a lubricant. It also comprises the "lead" in pencils.

The diamond lattice (Figure 3a) contains tetrahedral carbon atoms in

an infinite three-dimensional network. Graphite is also an infinite three-dimensional network, but it is made up of planar offset layers of trigonal carbons forming fused hexagonal rings (Figure 3b). The C-C bonds within

Figure 2. B 12 icosahedron.

Figure 3a. Portion of the structure of diamond. This structure repeats infinitely in all directions.

a layer are shorter than those of diamond, and are much shorter than the separation between the graphite layers. The weak, nonbonding, interaction between the layers, allowing them to easily slide over each other, accounts for the lubricating properties of graphite.

Diamond and graphite are nonmolecular allotropes of carbon. A range of molecular allotropes of carbon (the fullerenes) has been known since the discovery in 1985 of C 60 (Figure 4). The sixty carbon atoms approximate a sphere of condensed five- and six-membered rings. Although initially found in the laboratory, fullerenes have since been shown to occur in nature at low concentrations. C 60 and C 70 are generally the most abundant and readily isolated fullerenes.

In 1991 carbon nanotubes were discovered. They are more flexible and stronger than commercially available carbon fibers, and can be conductors or semiconductors. Although the mechanism of their formation has not been determined, they can be thought of as the result of "rolling up" a section of a graphite sheet and capping the ends with a hemisphere of C 60 , C 70 , or another molecular allotrope fragment. Five- or seven-membered rings can be incorporated among the six-membered rings, leading to an almost infinite range of helical, toroidal, and corkscrew-shaped tubes, all with different mechanical strengths and conductivities.

Figure 3b. Portion of the structure of graphite. This structure repeats infinitely in all directions.

Figure 4. A fullerene allotrope of C 60 .

Tin is a relatively low melting (232°C) material that exists in two allotropic forms at room temperature and pressure, α -Sn (gray tin) and β -Sn (white tin). α -Sn is the stable form below 13°C and has the diamond structure (Figure 3a). White, or β -Sn is metallic and has a distorted close-packed lattice.

Group 15

There are two allotropic elements in Group 15, phosphorus and arsenic . Phosphorus exists in several allotropic forms. The main ones (and those from which the others are derived) are white, red, and black (the thermodynamically stable form at room temperature). Only white and red phosphorus are of industrial importance. Phosphorus was first produced as the common white phosphorus, which is the most volatile , most reactive, and most toxic, but the least thermodynamically stable form of phosphorus, α -P 4 . It coverts to a polymorphic form, β -P 4 , at −76.9°C. White phosphorus is a waxy, nonconductor and reacts with air—the phosphorescent reaction of oxygen with the vapor above the solid producing the yellow-green chemiluminescent light, which gives phosphorus its name (after the Greek god, Eosphoros, the morning star, the bringer of light). The phosphorus in commercial use is amorphous red phosphorus, produced by heating white phosphorus in the absence of air at about 300°C. It melts around 600°C and was long thought to contain polymers formed by breaking a P-P bond of each P 4 tetrahedron of white phosphorus then linking the "opened" tetrahedra (Figures 5a and 5b).

A variety of crystalline modifications (tetragonal red, triclinic red, cubic red), possibly with similar polymeric structures can also be prepared by heating amorphous red phosphorus at over 500°C.

The most thermodynamically stable, and least reactive, form of phosphorus is black phosphorus, which exists as three crystalline (orthorhombic-, rhombohedral- and metallic, or cubic) and one amorphous, allotrope. All are polymeric solids and are practically nonflammable. Both orthorhombic and rhombohedral phosphorus appear black and graphitic, consistent with their layered structures.

Figure 5a. Linkage of P 4 units in red phosphorus.

A violet crystalline allotrope, monoclinic phosphorus, or Hittorf's phosphorus, after its discoverer, can be produced by a complicated thermal and electrolytic procedure. The structure is very complex, consisting of tubes of

Figure 5(b). Linkage of P 4 units in red phosphorus.

pentagonal cross section joined in pairs to form double layers, which are repeated through the crystal. The tubes are formed from cagelike P 8 and P 9 groups, linked by P 2 units.

At least six forms of solid arsenic have been reported, of which three are amorphous. The most stable and most common form of arsenic at room temperature is a brittle, steel-gray solid ( α -As) with a structure analogous to that of rhombohedral black phosphorus. Arsenic vapor contains tetrahedral As 4 molecules, which are thought to be present in the yellow unstable arsenic formed by condensation of the vapor. Arsenic occurs naturally as α -As and also as the mineral arsenolamprite, which may have the same structure as orthorhombic black phosphorus.

Group 16

There are only three allotropic elements in Group 16, oxygen, sulfur, and selenium. Only two oxygen allotropes are known—dinuclear "oxygen" (dioxygen, O 2 ) and trinuclear ozone (O 3 ) (Figure 6). Both are gases at room temperature and pressure. Dioxygen exists as a diradical (contains two unpaired electrons) and is the only allotrope of any element with unpaired electrons. Liquid and solid dioxygen are both pale blue because the absorption of light excites the molecule to a higher energy (and much more reactive) electronic state in which all electrons are paired ("singlet" oxygen). Gaseous dioxygen is probably also blue, but the low concentration of the species in the gas phase makes it difficult to observe.

Ozone is a V-shaped, triatomic dark blue gaseous molecule with a bond order of 1½. It is usually prepared from dioxygen by electric discharge (e.g., lightning) and can be detected by its characteristic "sharp" smell—from which it gets its name (after the Greekozein : to smell). Ozone is thermodynamically unstable and reverts spontaneously to dioxygen.

The dark blue color of O 3 is important because it arises from the intense absorption of red and ultraviolet (UV) light. This is the mechanism by which ozone in the atmosphere (the ozone layer) protects Earth from the Sun's UV radiation. After F 2 , ozone is the most powerful oxidant of all the elements.

Figure 6. Dioxygen and ozone, the allotropes of oxygen.

Figure 7. Sulfur allotrope, S 8 .

Sulfur (S) is second only to carbon in the number of known allotropes formed. The existence of at least twenty-two sulfur allotropes has been demonstrated. The simplest allotrope of sulfur is the violet disulfur molecule, S 2 , analogous to the dioxygen molecule. Unlike O 2 , however, S 2 does not occur naturally at room temperature and pressure. It is commonly generated in the vapor generated from sulfur at temperatures above 700°C. It has been detected by the Hubble Space Telescope in volcanic eruptions on Jupiter's satellite, Io.

The most thermodynamically stable of all of the sulfur allotropes and the form in which sulfur ordinarily exists is orthorhombic sulfur, α -S 8 , cyclooctasulfur, which contains puckered eight-membered rings, in which each sulfur atom is two-coordinate (Figure 7).

The second allotrope of sulfur to be discovered was cyclohexasulfur (sometimes called rhombohedral sulfur), first reported in 1891. It is the

densest of the sulfur allotropes and forms air-sensitive orange-red crystals containing chair-shaped, six-membered rings. Sulfur forms an extensive series of generally yellow crystalline allotropes, S n (where species with n up to 30 have been identified). The color of liquid sulfur changes from pale yellow to orange, then red and finally to black, near the boiling point (445°C). At about 159°C, the viscosity increases as polymeric sulfur is formed. The liquid is thought to contain chains of sulfur atoms, wound into helices.

Selenium (Se) also exists in several allotropic forms—gray (trigonal) selenium (containing Se n helical chain polymers), rhombohedral selenium (containing Se 6 molecules), three deep-red monoclinic forms— α -, β -, and γ -selenium (containing Se 8 molecules), amorphous red selenium, and black vitreous selenium, the form in industrial usage. The most thermodynamically stable and the densest form is gray (trigonal) selenium, which contains infinite helical chains of selenium atoms. All other forms revert to gray selenium on warming. In keeping with its density, gray selenium is regarded as metallic, and it is the only form of selenium that conducts electricity. A slight distortion of the helical structure would produce a cubic metallic lattice.

The trend from nonmetallic to metallic character upon going down the group is exemplified by the conductivities of these elements. Sulfur is an insulator, selenium and tellurium are semiconductors, while the conductivity of polonium is typical of a true metal . In addition, the conductivities of sulfur, selenium, and tellurium increase with increasing temperature, behavior typical of nonmetals, whereas that of polonium increases at lower temperatures, typical of metals.

From Wikipedia, the free encyclopedia

Eight allotropes of carbon: a) diamond, b) graphite, c) lonsdaleite, d)

C60 buckminsterfullerene, e) C540, Fullerite f) C70, g) amorphous carbon, and h) single-

walled carbon nanotube.

Carbon is capable of forming many allotropes due to its valency. Well-known forms of carbon include diamond and graphite. In recent decades many more allotropes and forms of carbon have been discovered and researched including ball shapes such as buckminsterfullerene and sheets such as graphene. Larger scale structures of carbon include nanotubes, nanobuds and nanoribbons. Other unusual forms of carbon exist at very high temperatures or extreme pressures. Around 500 hypothetical 3-periodic allotropes of carbon are known at the present time according to SACADA[1] database.

White phosphorus sample

White phosphorus, yellow phosphorus or simply tetraphosphorus (P4) exists as molecules made up of four atoms in a tetrahedral structure. The tetrahedral arrangement results in ring strain and instability. The molecule is described as consisting of six single P–P bonds. Two different crystalline forms are known. The α form is defined as the standard state of the element, but is actually metastable under standard conditions.[1] It has a body-centered cubic crystal structure, and transforms reversibly into the β form at 195.2 K. The β form is believed to have a hexagonal crystal structure.[2]

White phosphorus is a translucent waxy solid that quickly becomes yellow when exposed to light. For this reason it is also called yellow phosphorus. It glows greenish in the dark (when exposed to oxygen) and is highly flammable and pyrophoric (self-igniting) upon contact with air. It is toxic, causing severe liver damage on ingestion and phossy jaw from chronic ingestion or inhalation. The odour of combustion of this form has a characteristic garlic smell, and samples are commonly coated with white "diphosphorus pentoxide", which consists of P4O10tetrahedral with oxygen inserted between the phosphorus atoms and at their vertices. White phosphorus is only slightly soluble in water and can be stored under water. Indeed, white phosphorus is safe from self-igniting only when it is submerged in water. It is soluble in benzene, oils, carbon disulfide, and disulfur dichloride.

Production and applications[edit]

The white allotrope can be produced using several different methods. In the industrial process, phosphate rock is heated in an electric or fuel-fired furnace in the presence of carbonand silica.[3] Elemental phosphorus is then liberated as a vapour and can be collected under phosphoric acid. An idealized equation for this carbothermal reaction is shown for calcium phosphate (although phosphate rock contains substantial amounts of fluoroapatite):

2 Ca3(PO4)2 + 8 C → P4 + 8 CO2 + 6 Ca

Tetraphosphorus molecule

White phosphorus has an appreciable vapour pressure at ordinary temperatures. The vapour density indicates that the vapour is composed of

P4 molecules up to about 800 °C. Above that temperature, dissociation into P2 molecules occurs.

It ignites spontaneously in air at about 50 °C (122 °F), and at much lower temperatures if finely divided. This combustion gives phosphorus (V) oxide:

P

4 + 5 O

2 → P

4O

10

Because of this property, white phosphorus is used as a weapon.

Non-existence of cubic-P8[edit]

Although white phosphorus converts to the thermodynamically more stable red allotrope, the formation of the cubic P8 molecule is not observed in the condensed phase. Analogs of this hypothetical molecule have been prepared from phosphaalkynes.[4]

Red phosphorus[edit]

Red phosphorus

Red phosphorus structure

Red phosphorus may be formed by heating white phosphorus to 300 °C (572 °F) in the absence of air or by exposing white phosphorus to sunlight. Red phosphorus exists as an amorphous network. Upon further heating, the amorphous red phosphorus crystallizes. Red phosphorus does not ignite in air at temperatures below 240 °C (464 °F), whereas pieces of white phosphorus ignite at about 30 °C (86 °F). Ignition is spontaneous at room temperature with finely divided material.

Under standard conditions it is more stable than white phosphorus, but less stable than the thermodynamically stable black phosphorus. The standard enthalpy of formation of red phosphorus is -17.6 kJ/mol.[1]

Applications[edit]

Red phosphorus can be used as a very effective flame retardant, especially in thermoplastics (e.g. polyamide) and thermosets (e.g. epoxy resins or polyurethanes). The flame retarding effect is based on the formation of polyphosphoric acid. Together with the organic polymer material, this acid creates a char which prevents the propagation of the flames. The safety risks associated with phosphine generation and friction sensitivity of red phosphorus can be effectively reduced by stabilization and micro-encapsulation. For easier handling, red phosphorus is often used in form of dispersions or masterbatches in various carrier systems. However, for electronic/electrical systems, red phosphorus flame retardant has been effectively banned by major OEMs due to its tendency to induce premature failures. There have been two issues over the years: the first was red phosphorus in epoxy molding compounds inducing elevated leakage current in semiconductor devices[5] and the second was acceleration of hydrolysis reactions in PBT insulating material.[6]

Hittorf's violet phosphorus[edit]

Violet phosphorus (right) by a sample of red phosphorus (left)

Violet phosphorus structure

Hitorff phosphorus structure

Monoclinic phosphorus, or violet phosphorus, is also known as Hittorf's metallic phosphorus.[7][8] In 1865, Johann Wilhelm Hittorf heated red phosphorus in a sealed tube at 530 °C. The upper part of the tube was kept at 444 °C. Brilliant opaque monoclinic, or rhombohedral, crystals sublime. Violet phosphorus can also be prepared by dissolving white phosphorus in molten lead in a sealed tube at 500 °C for 18 hours. Upon slow cooling, Hittorf's allotrope crystallises out. The crystals can be revealed by dissolving the lead in dilute nitric acid followed by boiling in concentrated hydrochloric acid.[9] In addition, a fibrous form exists with similar phosphorus cages.

Reactions of violet phosphorus[edit]

It does not ignite in air until heated to 300 °C and is insoluble in all solvents. It is not attacked by alkali and only slowly reacts with halogens. It can be oxidised by nitric acid to phosphoric acid.

If it is heated in an atmosphere of inert gas, for example nitrogen or carbon dioxide, it sublimes and the vapour condenses as white phosphorus. If it is heated in a vacuum and the vapour condensed rapidly, violet phosphorus is obtained. It would appear that violet phosphorus is a polymer of high relative molecular mass, which on heating breaks down into P2 molecules. On cooling, these would normally dimerize to give P4 molecules (i.e. white phosphorus) but, in vacuo, they link up again to form the polymeric violet allotrope.

Black phosphorus[edit]

Black phosphorus ampoule

Black phosphorus

Black phosphorus structure

See also: phosphorene

Black phosphorus is the thermodynamically stable form of phosphorus at room temperature and pressure, with a heat of formation of -39.3 kJ/mol (relative to white phosphorus which is defined as the standard state).[1] It is obtained by heating white phosphorus under high pressures (12,000 atmospheres). In appearance, properties, and structure, black phosphorus is very much like graphitewith both being black and flaky, a conductor of electricity, and having puckered sheets of linked atoms,[10] . Phonons, photons, and electrons in layered black phosphorus structures behave in a highly anisotropic manner within the plane of layers, exhibiting strong potential for applications to thin film electronics and infrared optoelectronics.[11]

Black phosphorus has an orthorhombic structure and is the least reactive allotrope, a result of its lattice of interlinked six-membered rings where each atom is bonded to three other atoms.[12][13]Black and red phosphorus can also take a cubic crystal lattice structure.[14]. The first high-pressure

synthesis of black phosphorus crystals was made by the physicist Percy Williams Bridgman in 1914[15]. A recent synthesis of black phosphorus using metal salts as catalysts has been reported.[16]

The similarities to graphite also include the possibility of scotch-tape delamination (exfoliation), resulting in phosphorene, a graphene-like 2D material with excellent charge and thermal transport properties.Highly anisotropic thermal conductivity has been measured in three major principal crystal orientations.[17] [18] Exfoliated black phosphorus sublimes at 400 °C in vacuum.[19] It gradually oxidizes when exposed to water in the presence of oxygen, which is a concern when contemplating it as a material for the manufacture of transistors, for example.[20][21]

Diphosphorus[edit] Main article: Diphosphorus

Structure of diphosphorus

Diphosphorus molecule

The diphosphorus allotrope (P2) can normally be obtained only under extreme conditions (for example, from P4 at 1100 kelvin). In 2006, the diatomic molecule was generated in homogenous solution under normal conditions with the use of transition metal complexes (for example, tungstenand niobium).[22]

Diphosphorus is the gaseous form of phosphorus, and the thermodynamically stable form between 1200 °C and 2000 °C. The dissociation of tetraphosphorus (P

4) begins at lower temperature: the percentage of P

2 at 800 °C is ≈ 1%. At temperatures above about 2000 °C, the diphosphorus molecule begins to dissociate into atomic phosphorus.

Phosphorus nanorods[edit] P12 nanorod polymers were isolated from CuI-P complexes using low temperature treatment.[23]

Red/brown phosphorus was shown to be stable in air for several weeks and have significantly different properties from red phosphorus. Electron microscopy showed that red/brown phosphorus forms long, parallel nanorods with a diameter between 3.4 Å and 4.7 Å.[23]

Properties[edit]

Properties of some allotropes of phosphorus[24][25]

Form white(α) white(β) violet black

Symmetry Body-centred cubic Triclinic Monoclinic Orthorhombic

Pearson symbol

aP24 mP84 oS8

Space group I43m P1 No.2 P2/c No.13 Cmca No.64

Density (g/cm3) 1.828 1.88 2.36 2.69

Bandgap (eV) 2.1

1.5 0.34

Refractive index 1.8244

2.6 2.4

References[edit]

1. ^ Jump up to:a b c Housecroft, C. E.; Sharpe, A. G. (2004). Inorganic Chemistry (2nd ed.). Prentice Hall. p. 392. ISBN 978-0130399137.

2. Jump up^ Durif, M.-T. Averbuch-Pouchot ; A. (1996). Topics in phosphate chemistry. Singapore [u.a.]: World Scientific. p. 3. ISBN 981-02-2634-9.

3. Jump up^ Threlfall, R.E., (1951). 100 years of Phosphorus Making: 1851–1951. Oldbury: Albright and Wilson Ltd

4. Jump up^ Streubel, Rainer (1995). "Phosphaalkyne Cyclooligomers: From Dimers to Hexamers—First Steps on the Way to Phosphorus–Carbon Cage Compounds". Angewandte Chemie International Edition in English. 34 (4): 436–438. doi:10.1002/anie.199504361.

5. Jump up^ Craig Hillman, Red Phosphorus Induced Failures in Encapsulated Circuits, https://www.dfrsolutions.com/hubfs/Resources/services/Red-Phosphorus-Induced-Failures-in-Encapsulated-Circuits.pdf?t=1513022462214

6. Jump up^ Dock Brown, The Return of the Red Retardant, SMTAI 2015, https://www.dfrsolutions.com/hubfs/Resources/services/The-Return-of-the-Red-Retardant.pdf?t=1513022462214

7. Jump up^ Curry, Roger. "Hittorf`s Metallic Phosphorus of 1865". LATERAL SCIENCE. Retrieved 16 November 2014.

8. Jump up^ Monoclinic phosphorus formed from vapor in the presence of an alkali metal U.S. Patent 4,620,968

9. Jump up^ Hittorf, W. (1865). "Zur Kenntniss des Phosphors". Annalen der Physik. 202 (10): 193–228. Bibcode:1865AnP...202..193H. doi:10.1002/andp.18652021002.

10. Jump up^ Korolkov, Vladimir V.; Timokhin, Ivan G.; Haubrichs, Rolf; Smith, Emily F.; Yang, Lixu; Yang, Sihai; Champness, Neil R.; Schröder, Martin; Beton, Peter H. (2017-11-09). "Supramolecular networks stabilise and functionalise black phosphorus". Nature Communications. 8 (1). doi:10.1038/s41467-017-01797-6. ISSN 2041-1723.

11. Jump up^ Allain, A.; Kang, J.; Banerjee, K.; Kis, A., Electrical contacts to two-dimensional semiconductors. Nat. Mater. 2015, volume 14, pp. 1195-1205. doi:10.1038/nmat4452

12. Jump up^ Brown, A.; Rundqvist, S. (1965). "Refinement of the crystal structure of black phosphorus". Acta Crystallographica. 19 (4): 684–685. doi:10.1107/S0365110X65004140.

13. Jump up^ Cartz, L.; Srinivasa, S. R.; Riedner, R. J.; Jorgensen, J. D.; Worlton, T. G. (1979). "Effect of pressure on bonding in black phosphorus". The Journal of Chemical Physics. 71 (4): 1718. Bibcode:1979JChPh..71.1718C. doi:10.1063/1.438523.

14. Jump up^ Ahuja, Rajeev (2003). "Calculated high pressure crystal structure transformations for phosphorus". Physica status solidi (b). 235 (2): 282–287. Bibcode:2003PSSBR.235..282A. doi:10.1002/pssb.200301569.

15. Jump up^ Bridgman, P. W. (1914-07-01). "TWO NEW MODIFICATIONS OF PHOSPHORUS". Journal of the American Chemical Society. 36 (7): 1344–1363. doi:10.1021/ja02184a002. ISSN 0002-7863.

16. Jump up^ Lange, Stefan; Schmidt, Peer; Nilges, Tom (2007). "Au3SnP7@Black Phosphorus: An Easy Access to Black Phosphorus". Inorganic Chemistry. 46 (10): 4028–35. doi:10.1021/ic062192q. PMID 17439206.

17. Jump up^ Kang, J.; Ke, M.; Hu, Y. "Ionic Intercalation in Two-Dimensional van der Waals Materials: In Situ Characterization and Electrochemical Control of the Anisotropic Thermal Conductivity of Black Phosphorus". Nano Letters. 17: 1431. Bibcode:2017NanoL..17.1431K. doi:10.1021/acs.nanolett.6b04385.

18. Jump up^ Smith, B.; Vermeersch, B.; Carrete, J.; Ou, E.; Kim, J.; Li, S. "Temperature and Thickness Dependences of the Anisotropic In-Plane Thermal Conductivity of Black Phosphorus". Adv Mater. 29: 1603756.

19. Jump up^ Liu, Xiaolong D.; Wood, Joshua D.; Chen, Kan-Sheng; Cho, EunKyung; Hersam, Mark C. (9 February 2015). "In Situ Thermal Decomposition of Exfoliated Two-Dimensional Black Phosphorus". Journal of Physical Chemistry Letters. 6: 773–778. doi:10.1021/acs.jpclett.5b00043.

20. Jump up^ Wood, Joshua D.; Wells, Spencer A.; Jariwala, Deep; Chen, Kan-Sheng; Cho, EunKyung; Sangwan, Vinod K.; Liu, Xiaolong; Lauhon, Lincoln J.; Marks, Tobin J.; Hersam, Mark C. (7 November 2014). "Effective Passivation of Exfoliated Black Phosphorus Transistors against Ambient Degradation". Nano Letters. 14 (12): 6964–6970. arXiv:1411.2055 . Bibcode:2014NanoL..14.6964W. doi:10.1021/nl5032293. PMID 25380142.

21. Jump up^ Wu, Ryan J.; Topsakal, Mehmet; Low, Tony; Robbins, Matthew C.; Haratipour, Nazila; Jeong, Jong Seok; Wentzcovitch, Renata M.; Koester, Steven J.; Mkhoyan, K. Andre (2015-11-01). "Atomic and electronic structure of exfoliated black phosphorus". Journal of Vacuum Science & Technology A. 33 (6): 060604. doi:10.1116/1.4926753. ISSN 0734-2101.

22. Jump up^ Piro, Na; Figueroa, Js; Mckellar, Jt; Cummins, Cc (2006). "Triple-bond reactivity of diphosphorus molecules". Science. 313 (5791): 1276–9. Bibcode:2006Sci...313.1276P. doi:10.1126/science.1129630. PMID 16946068.

23. ^ Jump up to:a b Pfitzner, A; Bräu, Mf; Zweck, J; Brunklaus, G; Eckert, H (Aug 2004). "Phosphorus nanorods – two allotropic modifications of a long-known element". Angewandte Chemie International Edition in English. 43 (32): 4228–31. doi:10.1002/anie.200460244. PMID 15307095.

24. Jump up^ A. Holleman; N. Wiberg (1985). "XV 2.1.3". Lehrbuch der Anorganischen Chemie (33 ed.). de Gruyter. ISBN 3-11-012641-9.

25. Jump up^ Berger, L. I. (1996). Semiconductor materials. CRC Press. p. 84. ISBN 0-8493-8912-7.

External links[edit] White phosphorus

White Phophorus at The Periodic Table of Videos (University of Nottingham)

More about White Phosphorus (and phosphorus pentoxide) at The Periodic Table of Videos (University of Nottingham)

Categories:

Allotropy

Phosphorus

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White phosphorus sample

White phosphorus, yellow phosphorus or simply tetraphosphorus (P4) exists as molecules made up of four atoms in a tetrahedral structure. The tetrahedral arrangement results in ring strain and instability. The molecule is described as consisting of six single P–P bonds. Two different crystalline forms are known. The α form is defined as the standard state of the element, but is actually metastable under standard conditions.[1] It has a body-centered cubic crystal structure, and transforms reversibly into the β form at 195.2 K. The β form is believed to have a hexagonal crystal structure.[2]

White phosphorus is a translucent waxy solid that quickly becomes yellow when exposed to light. For this reason it is also called yellow phosphorus. It glows

greenish in the dark (when exposed to oxygen) and is highly flammable and pyrophoric (self-igniting) upon contact with air. It is toxic, causing severe liver damage on ingestion and phossy jaw from chronic ingestion or inhalation. The odour of combustion of this form has a characteristic garlic smell, and samples are commonly coated with white "diphosphorus pentoxide", which consists of P4O10tetrahedral with oxygen inserted between the phosphorus atoms and at their vertices. White phosphorus is only slightly soluble in water and can be stored under water. Indeed, white phosphorus is safe from self-igniting only when it is submerged in water. It is soluble in benzene, oils, carbon disulfide, and disulfur dichloride.

Production and applications[edit]

The white allotrope can be produced using several different methods. In the industrial process, phosphate rock is heated in an electric or fuel-fired furnace in the presence of carbonand silica.[3] Elemental phosphorus is then liberated as a vapour and can be collected under phosphoric acid. An idealized equation for this carbothermal reaction is shown for calcium phosphate (although phosphate rock contains substantial amounts of fluoroapatite):

2 Ca3(PO4)2 + 8 C → P4 + 8 CO2 + 6 Ca

Tetraphosphorus molecule

White phosphorus has an appreciable vapour pressure at ordinary temperatures. The vapour density indicates that the vapour is composed of P4 molecules up to about 800 °C. Above that temperature, dissociation into P2 molecules occurs.

It ignites spontaneously in air at about 50 °C (122 °F), and at much lower temperatures if finely divided. This combustion gives phosphorus (V) oxide:

P

4 + 5 O

2 → P

4O

10

Because of this property, white phosphorus is used as a weapon.

Non-existence of cubic-P8[edit]

Although white phosphorus converts to the thermodynamically more stable red allotrope, the formation of the cubic P8 molecule is not observed in the condensed phase. Analogs of this hypothetical molecule have been prepared from phosphaalkynes.[4]

Red phosphorus[edit]

Red phosphorus

Red phosphorus structure

Red phosphorus may be formed by heating white phosphorus to 300 °C (572 °F) in the absence of air or by exposing white phosphorus to sunlight. Red phosphorus exists as an amorphous network. Upon further heating, the amorphous red phosphorus crystallizes. Red phosphorus does not ignite in air at temperatures below 240 °C (464 °F), whereas pieces of white phosphorus ignite at about 30 °C (86 °F). Ignition is spontaneous at room temperature with finely divided material.

Under standard conditions it is more stable than white phosphorus, but less stable than the thermodynamically stable black phosphorus. The standard enthalpy of formation of red phosphorus is -17.6 kJ/mol.[1]

Applications[edit]

Red phosphorus can be used as a very effective flame retardant, especially in thermoplastics (e.g. polyamide) and thermosets (e.g. epoxy resins or polyurethanes). The flame retarding effect is based on the formation of polyphosphoric acid. Together with the organic polymer material, this acid creates a char which prevents the propagation of the

flames. The safety risks associated with phosphine generation and friction sensitivity of red phosphorus can be effectively reduced by stabilization and micro-encapsulation. For easier handling, red phosphorus is often used in form of dispersions or masterbatches in various carrier systems. However, for electronic/electrical systems, red phosphorus flame retardant has been effectively banned by major OEMs due to its tendency to induce premature failures. There have been two issues over the years: the first was red phosphorus in epoxy molding compounds inducing elevated leakage current in semiconductor devices[5] and the second was acceleration of hydrolysis reactions in PBT insulating material.[6]

Hittorf's violet phosphorus[edit]

Violet phosphorus (right) by a sample of red phosphorus (left)

Violet phosphorus structure

Hitorff phosphorus structure

Monoclinic phosphorus, or violet phosphorus, is also known as Hittorf's metallic phosphorus.[7][8] In 1865, Johann Wilhelm Hittorf heated red phosphorus in a sealed tube at 530 °C. The upper part of the tube was kept at 444 °C. Brilliant opaque monoclinic, or rhombohedral, crystals sublime. Violet phosphorus can also be prepared by dissolving white phosphorus in molten lead in a sealed tube at 500 °C for 18 hours. Upon slow cooling, Hittorf's allotrope crystallises out. The crystals can be revealed by dissolving the lead in dilute nitric acid followed by boiling in concentrated hydrochloric acid.[9] In addition, a fibrous form exists with similar phosphorus cages.

Reactions of violet phosphorus[edit]

It does not ignite in air until heated to 300 °C and is insoluble in all solvents. It is not attacked by alkali and only slowly reacts with halogens. It can be oxidised by nitric acid to phosphoric acid.

If it is heated in an atmosphere of inert gas, for example nitrogen or carbon dioxide, it sublimes and the vapour condenses as white phosphorus. If it is heated in a vacuum and the vapour condensed rapidly, violet phosphorus is obtained. It would appear that violet phosphorus is a polymer of high relative molecular mass, which on heating breaks down into P2 molecules. On cooling, these would normally dimerize to give P4 molecules (i.e. white phosphorus) but, in vacuo, they link up again to form the polymeric violet allotrope.

Black phosphorus[edit]

Black phosphorus ampoule

Black phosphorus

Black phosphorus structure

See also: phosphorene

Black phosphorus is the thermodynamically stable form of phosphorus at room temperature and pressure, with a heat of formation of -39.3 kJ/mol (relative to white phosphorus which is defined as the standard state).[1] It is obtained by heating white phosphorus under high pressures (12,000 atmospheres). In appearance, properties, and structure, black phosphorus is very much like graphitewith both being black and flaky, a conductor of electricity, and having puckered sheets of linked atoms,[10] . Phonons, photons, and electrons in layered black phosphorus structures behave in a highly anisotropic manner within the plane of layers, exhibiting strong potential for applications to thin film electronics and infrared optoelectronics.[11]

Black phosphorus has an orthorhombic structure and is the least reactive allotrope, a result of its lattice of interlinked six-membered rings where each atom is bonded to three other atoms.[12][13]Black and red phosphorus can also take a cubic crystal lattice structure.[14]. The first high-pressure synthesis of black phosphorus crystals was made by the physicist Percy Williams Bridgman in 1914[15]. A recent synthesis of black phosphorus using metal salts as catalysts has been reported.[16]

The similarities to graphite also include the possibility of scotch-tape delamination (exfoliation), resulting in phosphorene, a graphene-like 2D material with excellent charge and thermal transport properties.Highly anisotropic thermal conductivity has been measured in three major principal crystal orientations.[17] [18] Exfoliated black phosphorus sublimes at 400 °C in vacuum.[19] It gradually oxidizes when exposed to water in the presence of oxygen, which is a concern when contemplating it as a material for the manufacture of transistors, for example.[20][21]

Diphosphorus[edit] Main article: Diphosphorus

Structure of diphosphorus

Diphosphorus molecule

The diphosphorus allotrope (P2) can normally be obtained only under extreme conditions (for example, from P4 at 1100 kelvin). In 2006, the diatomic molecule was generated in homogenous solution under normal conditions with the use of transition metal complexes (for example, tungstenand niobium).[22]

Diphosphorus is the gaseous form of phosphorus, and the thermodynamically stable form between 1200 °C and 2000 °C. The dissociation of tetraphosphorus (P

4) begins at lower temperature: the percentage of P

2 at 800 °C is ≈ 1%. At temperatures above about 2000 °C, the diphosphorus molecule begins to dissociate into atomic phosphorus.

Phosphorus nanorods[edit] P12 nanorod polymers were isolated from CuI-P complexes using low temperature treatment.[23]

Red/brown phosphorus was shown to be stable in air for several weeks and have significantly different properties from red phosphorus. Electron microscopy showed that red/brown phosphorus forms long, parallel nanorods with a diameter between 3.4 Å and 4.7 Å.[23]

Properties[edit]

Properties of some allotropes of phosphorus[24][25]

Form white(α) white(β) violet black

Symmetry Body-centred cubic Triclinic Monoclinic Orthorhombic

Pearson symbol

aP24 mP84 oS8

Space group I43m P1 No.2 P2/c No.13 Cmca No.64

Density (g/cm3) 1.828 1.88 2.36 2.69

Bandgap (eV) 2.1

1.5 0.34

Refractive index 1.8244

2.6 2.4

References[edit]

1. ^ Jump up to:a b c Housecroft, C. E.; Sharpe, A. G. (2004). Inorganic Chemistry (2nd ed.). Prentice Hall. p. 392. ISBN 978-0130399137.

2. Jump up^ Durif, M.-T. Averbuch-Pouchot ; A. (1996). Topics in phosphate chemistry. Singapore [u.a.]: World Scientific. p. 3. ISBN 981-02-2634-9.

3. Jump up^ Threlfall, R.E., (1951). 100 years of Phosphorus Making: 1851–1951. Oldbury: Albright and Wilson Ltd

4. Jump up^ Streubel, Rainer (1995). "Phosphaalkyne Cyclooligomers: From Dimers to Hexamers—First Steps on the Way to Phosphorus–Carbon Cage

Compounds". Angewandte Chemie International Edition in English. 34 (4): 436–438. doi:10.1002/anie.199504361.

5. Jump up^ Craig Hillman, Red Phosphorus Induced Failures in Encapsulated Circuits, https://www.dfrsolutions.com/hubfs/Resources/services/Red-Phosphorus-Induced-Failures-in-Encapsulated-Circuits.pdf?t=1513022462214

6. Jump up^ Dock Brown, The Return of the Red Retardant, SMTAI 2015, https://www.dfrsolutions.com/hubfs/Resources/services/The-Return-of-the-Red-Retardant.pdf?t=1513022462214

7. Jump up^ Curry, Roger. "Hittorf`s Metallic Phosphorus of 1865". LATERAL SCIENCE. Retrieved 16 November 2014.

8. Jump up^ Monoclinic phosphorus formed from vapor in the presence of an alkali metal U.S. Patent 4,620,968

9. Jump up^ Hittorf, W. (1865). "Zur Kenntniss des Phosphors". Annalen der Physik. 202 (10): 193–228. Bibcode:1865AnP...202..193H. doi:10.1002/andp.18652021002.

10. Jump up^ Korolkov, Vladimir V.; Timokhin, Ivan G.; Haubrichs, Rolf; Smith, Emily F.; Yang, Lixu; Yang, Sihai; Champness, Neil R.; Schröder, Martin; Beton, Peter H. (2017-11-09). "Supramolecular networks stabilise and functionalise black phosphorus". Nature Communications. 8 (1). doi:10.1038/s41467-017-01797-6. ISSN 2041-1723.

11. Jump up^ Allain, A.; Kang, J.; Banerjee, K.; Kis, A., Electrical contacts to two-dimensional semiconductors. Nat. Mater. 2015, volume 14, pp. 1195-1205. doi:10.1038/nmat4452

12. Jump up^ Brown, A.; Rundqvist, S. (1965). "Refinement of the crystal structure of black phosphorus". Acta Crystallographica. 19 (4): 684–685. doi:10.1107/S0365110X65004140.

13. Jump up^ Cartz, L.; Srinivasa, S. R.; Riedner, R. J.; Jorgensen, J. D.; Worlton, T. G. (1979). "Effect of pressure on bonding in black phosphorus". The Journal of Chemical Physics. 71 (4): 1718. Bibcode:1979JChPh..71.1718C. doi:10.1063/1.438523.

14. Jump up^ Ahuja, Rajeev (2003). "Calculated high pressure crystal structure transformations for phosphorus". Physica status solidi (b). 235 (2): 282–287. Bibcode:2003PSSBR.235..282A. doi:10.1002/pssb.200301569.

15. Jump up^ Bridgman, P. W. (1914-07-01). "TWO NEW MODIFICATIONS OF PHOSPHORUS". Journal of the American Chemical Society. 36 (7): 1344–1363. doi:10.1021/ja02184a002. ISSN 0002-7863.

16. Jump up^ Lange, Stefan; Schmidt, Peer; Nilges, Tom (2007). "Au3SnP7@Black Phosphorus: An Easy Access to Black Phosphorus". Inorganic Chemistry. 46 (10): 4028–35. doi:10.1021/ic062192q. PMID 17439206.

17. Jump up^ Kang, J.; Ke, M.; Hu, Y. "Ionic Intercalation in Two-Dimensional van der Waals Materials: In Situ Characterization and Electrochemical Control of the Anisotropic Thermal Conductivity of Black Phosphorus". Nano Letters. 17: 1431. Bibcode:2017NanoL..17.1431K. doi:10.1021/acs.nanolett.6b04385.

18. Jump up^ Smith, B.; Vermeersch, B.; Carrete, J.; Ou, E.; Kim, J.; Li, S. "Temperature and Thickness Dependences of the Anisotropic In-Plane Thermal Conductivity of Black Phosphorus". Adv Mater. 29: 1603756.

19. Jump up^ Liu, Xiaolong D.; Wood, Joshua D.; Chen, Kan-Sheng; Cho, EunKyung; Hersam, Mark C. (9 February 2015). "In Situ Thermal

Decomposition of Exfoliated Two-Dimensional Black Phosphorus". Journal of Physical Chemistry Letters. 6: 773–778. doi:10.1021/acs.jpclett.5b00043.

20. Jump up^ Wood, Joshua D.; Wells, Spencer A.; Jariwala, Deep; Chen, Kan-Sheng; Cho, EunKyung; Sangwan, Vinod K.; Liu, Xiaolong; Lauhon, Lincoln J.; Marks, Tobin J.; Hersam, Mark C. (7 November 2014). "Effective Passivation of Exfoliated Black Phosphorus Transistors against Ambient Degradation". Nano Letters. 14 (12): 6964–6970. arXiv:1411.2055 . Bibcode:2014NanoL..14.6964W. doi:10.1021/nl5032293. PMID 25380142.

21. Jump up^ Wu, Ryan J.; Topsakal, Mehmet; Low, Tony; Robbins, Matthew C.; Haratipour, Nazila; Jeong, Jong Seok; Wentzcovitch, Renata M.; Koester, Steven J.; Mkhoyan, K. Andre (2015-11-01). "Atomic and electronic structure of exfoliated black phosphorus". Journal of Vacuum Science & Technology A. 33 (6): 060604. doi:10.1116/1.4926753. ISSN 0734-2101.

22. Jump up^ Piro, Na; Figueroa, Js; Mckellar, Jt; Cummins, Cc (2006). "Triple-bond reactivity of diphosphorus molecules". Science. 313 (5791): 1276–9. Bibcode:2006Sci...313.1276P. doi:10.1126/science.1129630. PMID 16946068.

23. ^ Jump up to:a b Pfitzner, A; Bräu, Mf; Zweck, J; Brunklaus, G; Eckert, H (Aug 2004). "Phosphorus nanorods – two allotropic modifications of a long-known element". Angewandte Chemie International Edition in English. 43 (32): 4228–31. doi:10.1002/anie.200460244. PMID 15307095.

24. Jump up^ A. Holleman; N. Wiberg (1985). "XV 2.1.3". Lehrbuch der Anorganischen Chemie (33 ed.). de Gruyter. ISBN 3-11-012641-9.

25. Jump up^ Berger, L. I. (1996). Semiconductor materials. CRC Press. p. 84. ISBN 0-8493-8912-7.

External links[edit] White phosphorus

White Phophorus at The Periodic Table of Videos (University of Nottingham)

More about White Phosphorus (and phosphorus pentoxide) at The Periodic Table of Videos (University of Nottingham)

Categories:

Allotropy

Phosphorus

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This page was last edited on 31 January 2018, at 03:09. Text is available under the Creative Commons Attribution-ShareAlike License; additional terms may

apply. By using this site, you agree to the Terms of Use and Privacy Policy. Wikipedia® is a

registered trademark of the Wikimedia Foundation, Inc., a non-profit

White phosphorus sample

White phosphorus, yellow phosphorus or simply tetraphosphorus (P4) exists as molecules made up of four atoms in a tetrahedral structure. The tetrahedral arrangement results in ring strain and instability. The molecule is described as consisting of six single P–P bonds. Two different crystalline forms are known. The α form is defined as the standard state of the element, but is actually metastable under standard conditions.[1] It has a body-centered cubic crystal structure, and transforms reversibly into the β form at 195.2 K. The β form is believed to have a hexagonal crystal structure.[2]

White phosphorus is a translucent waxy solid that quickly becomes yellow when exposed to light. For this reason it is also called yellow phosphorus. It glows greenish in the dark (when exposed to oxygen) and is highly flammable and pyrophoric (self-igniting) upon contact with air. It is toxic, causing severe liver damage on ingestion and phossy jaw from chronic ingestion or inhalation. The odour of combustion of this form has a characteristic garlic smell, and samples are commonly coated with white "diphosphorus pentoxide", which consists of P4O10tetrahedral with oxygen inserted between the phosphorus atoms and at their vertices. White phosphorus is only slightly soluble in water and can be stored under water. Indeed, white phosphorus is safe from self-igniting only when it is submerged in water. It is soluble in benzene, oils, carbon disulfide, and disulfur dichloride.

Production and applications[edit]

The white allotrope can be produced using several different methods. In the industrial process, phosphate rock is heated in an electric or fuel-fired furnace in the presence of carbonand silica.[3] Elemental phosphorus is then liberated as a vapour and can be collected under phosphoric acid. An idealized equation for

this carbothermal reaction is shown for calcium phosphate (although phosphate rock contains substantial amounts of fluoroapatite):

2 Ca3(PO4)2 + 8 C → P4 + 8 CO2 + 6 Ca

Tetraphosphorus molecule

White phosphorus has an appreciable vapour pressure at ordinary temperatures. The vapour density indicates that the vapour is composed of P4 molecules up to about 800 °C. Above that temperature, dissociation into P2 molecules occurs.

It ignites spontaneously in air at about 50 °C (122 °F), and at much lower temperatures if finely divided. This combustion gives phosphorus (V) oxide:

P

4 + 5 O

2 → P

4O

10

Because of this property, white phosphorus is used as a weapon.

Non-existence of cubic-P8[edit]

Although white phosphorus converts to the thermodynamically more stable red allotrope, the formation of the cubic P8 molecule is not observed in the condensed phase. Analogs of this hypothetical molecule have been prepared from phosphaalkynes.[4]

Red phosphorus[edit]

Red phosphorus

Red phosphorus structure

Red phosphorus may be formed by heating white phosphorus to 300 °C (572 °F) in the absence of air or by exposing white phosphorus to sunlight. Red phosphorus exists as an amorphous network. Upon further heating, the amorphous red phosphorus crystallizes. Red phosphorus does not ignite in air at temperatures below 240 °C (464 °F), whereas pieces of white phosphorus ignite at about 30 °C (86 °F). Ignition is spontaneous at room temperature with finely divided material.

Under standard conditions it is more stable than white phosphorus, but less stable than the thermodynamically stable black phosphorus. The standard enthalpy of formation of red phosphorus is -17.6 kJ/mol.[1]

Applications[edit]

Red phosphorus can be used as a very effective flame retardant, especially in thermoplastics (e.g. polyamide) and thermosets (e.g. epoxy resins or polyurethanes). The flame retarding effect is based on the formation of polyphosphoric acid. Together with the organic polymer material, this acid creates a char which prevents the propagation of the flames. The safety risks associated with phosphine generation and friction sensitivity of red phosphorus can be effectively reduced by stabilization and micro-encapsulation. For easier handling, red phosphorus is often used in form of dispersions or masterbatches in various carrier systems. However, for electronic/electrical systems, red phosphorus flame retardant has been effectively banned by major OEMs due to its tendency to induce premature failures. There have been two issues over the years: the first was red phosphorus in epoxy molding compounds inducing elevated leakage current in semiconductor devices[5] and the second was acceleration of hydrolysis reactions in PBT insulating material.[6]

Hittorf's violet phosphorus[edit]

Violet phosphorus (right) by a sample of red phosphorus (left)

Violet phosphorus structure

Hitorff phosphorus structure

Monoclinic phosphorus, or violet phosphorus, is also known as Hittorf's metallic phosphorus.[7][8] In 1865, Johann Wilhelm Hittorf heated red phosphorus in a sealed tube at 530 °C. The upper part of the tube was kept at 444 °C. Brilliant opaque monoclinic, or rhombohedral, crystals sublime. Violet phosphorus can also be prepared by dissolving white phosphorus in molten lead in a sealed tube at 500 °C for 18 hours. Upon slow cooling, Hittorf's allotrope crystallises out. The crystals can be revealed by dissolving the lead in dilute nitric acid followed by boiling in concentrated hydrochloric acid.[9] In addition, a fibrous form exists with similar phosphorus cages.

Reactions of violet phosphorus[edit]

It does not ignite in air until heated to 300 °C and is insoluble in all solvents. It is not attacked by alkali and only slowly reacts with halogens. It can be oxidised by nitric acid to phosphoric acid.

If it is heated in an atmosphere of inert gas, for example nitrogen or carbon dioxide, it sublimes and the vapour condenses as white phosphorus. If it is heated in a vacuum and the vapour condensed rapidly, violet phosphorus is obtained. It would appear that violet phosphorus is a polymer of high relative molecular mass, which on heating breaks down into P2 molecules. On cooling, these would normally dimerize to give P4 molecules (i.e. white phosphorus) but, in vacuo, they link up again to form the polymeric violet allotrope.

Black phosphorus[edit]

Black phosphorus ampoule

Black phosphorus

Black phosphorus structure

See also: phosphorene

Black phosphorus is the thermodynamically stable form of phosphorus at room temperature and pressure, with a heat of formation of -39.3 kJ/mol (relative to white phosphorus which is defined as the standard state).[1] It is obtained by heating white phosphorus under high pressures (12,000 atmospheres). In appearance, properties, and structure, black phosphorus is very much like graphitewith both being black and flaky, a conductor of

electricity, and having puckered sheets of linked atoms,[10] . Phonons, photons, and electrons in layered black phosphorus structures behave in a highly anisotropic manner within the plane of layers, exhibiting strong potential for applications to thin film electronics and infrared optoelectronics.[11]

Black phosphorus has an orthorhombic structure and is the least reactive allotrope, a result of its lattice of interlinked six-membered rings where each atom is bonded to three other atoms.[12][13]Black and red phosphorus can also take a cubic crystal lattice structure.[14]. The first high-pressure synthesis of black phosphorus crystals was made by the physicist Percy Williams Bridgman in 1914[15]. A recent synthesis of black phosphorus using metal salts as catalysts has been reported.[16]

The similarities to graphite also include the possibility of scotch-tape delamination (exfoliation), resulting in phosphorene, a graphene-like 2D material with excellent charge and thermal transport properties.Highly anisotropic thermal conductivity has been measured in three major principal crystal orientations.[17] [18] Exfoliated black phosphorus sublimes at 400 °C in vacuum.[19] It gradually oxidizes when exposed to water in the presence of oxygen, which is a concern when contemplating it as a material for the manufacture of transistors, for example.[20][21]

Diphosphorus[edit] Main article: Diphosphorus

Structure of diphosphorus

Diphosphorus molecule

The diphosphorus allotrope (P2) can normally be obtained only under extreme conditions (for example, from P4 at 1100 kelvin). In 2006, the diatomic molecule was generated in homogenous solution under normal conditions with the use of transition metal complexes (for example, tungstenand niobium).[22]

Diphosphorus is the gaseous form of phosphorus, and the thermodynamically stable form between 1200 °C and 2000 °C. The dissociation of tetraphosphorus (P

4) begins at lower temperature: the percentage of P

2 at 800 °C is ≈ 1%. At temperatures above about 2000 °C, the diphosphorus molecule begins to dissociate into atomic phosphorus.

Phosphorus nanorods[edit] P12 nanorod polymers were isolated from CuI-P complexes using low temperature treatment.[23]

Red/brown phosphorus was shown to be stable in air for several weeks and have significantly different properties from red phosphorus. Electron microscopy showed that red/brown phosphorus forms long, parallel nanorods with a diameter between 3.4 Å and 4.7 Å.[23]

Properties[edit]

Properties of some allotropes of phosphorus[24][25]

Form white(α) white(β) violet black

Symmetry Body-centred cubic Triclinic Monoclinic Orthorhombic

Pearson symbol

aP24 mP84 oS8

Space group I43m P1 No.2 P2/c No.13 Cmca No.64

Density (g/cm3) 1.828 1.88 2.36 2.69

Bandgap (eV) 2.1

1.5 0.34

Refractive index 1.8244

2.6 2.4

References[edit]

1. ^ Jump up to:a b c Housecroft, C. E.; Sharpe, A. G. (2004). Inorganic Chemistry (2nd ed.). Prentice Hall. p. 392. ISBN 978-0130399137.

2. Jump up^ Durif, M.-T. Averbuch-Pouchot ; A. (1996). Topics in phosphate chemistry. Singapore [u.a.]: World Scientific. p. 3. ISBN 981-02-2634-9.

3. Jump up^ Threlfall, R.E., (1951). 100 years of Phosphorus Making: 1851–1951. Oldbury: Albright and Wilson Ltd

4. Jump up^ Streubel, Rainer (1995). "Phosphaalkyne Cyclooligomers: From Dimers to Hexamers—First Steps on the Way to Phosphorus–Carbon Cage Compounds". Angewandte Chemie International Edition in English. 34 (4): 436–438. doi:10.1002/anie.199504361.

5. Jump up^ Craig Hillman, Red Phosphorus Induced Failures in Encapsulated Circuits, https://www.dfrsolutions.com/hubfs/Resources/services/Red-Phosphorus-Induced-Failures-in-Encapsulated-Circuits.pdf?t=1513022462214

6. Jump up^ Dock Brown, The Return of the Red Retardant, SMTAI 2015, https://www.dfrsolutions.com/hubfs/Resources/services/The-Return-of-the-Red-Retardant.pdf?t=1513022462214

7. Jump up^ Curry, Roger. "Hittorf`s Metallic Phosphorus of 1865". LATERAL SCIENCE. Retrieved 16 November 2014.

8. Jump up^ Monoclinic phosphorus formed from vapor in the presence of an alkali metal U.S. Patent 4,620,968

9. Jump up^ Hittorf, W. (1865). "Zur Kenntniss des Phosphors". Annalen der Physik. 202 (10): 193–228. Bibcode:1865AnP...202..193H. doi:10.1002/andp.18652021002.

10. Jump up^ Korolkov, Vladimir V.; Timokhin, Ivan G.; Haubrichs, Rolf; Smith, Emily F.; Yang, Lixu; Yang, Sihai; Champness, Neil R.; Schröder, Martin; Beton, Peter H. (2017-11-09). "Supramolecular networks stabilise and functionalise black phosphorus". Nature Communications. 8 (1). doi:10.1038/s41467-017-01797-6. ISSN 2041-1723.

11. Jump up^ Allain, A.; Kang, J.; Banerjee, K.; Kis, A., Electrical contacts to two-dimensional semiconductors. Nat. Mater. 2015, volume 14, pp. 1195-1205. doi:10.1038/nmat4452

12. Jump up^ Brown, A.; Rundqvist, S. (1965). "Refinement of the crystal structure of black phosphorus". Acta Crystallographica. 19 (4): 684–685. doi:10.1107/S0365110X65004140.

13. Jump up^ Cartz, L.; Srinivasa, S. R.; Riedner, R. J.; Jorgensen, J. D.; Worlton, T. G. (1979). "Effect of pressure on bonding in black phosphorus". The Journal of Chemical Physics. 71 (4): 1718. Bibcode:1979JChPh..71.1718C. doi:10.1063/1.438523.

14. Jump up^ Ahuja, Rajeev (2003). "Calculated high pressure crystal structure transformations for phosphorus". Physica status solidi (b). 235 (2): 282–287. Bibcode:2003PSSBR.235..282A. doi:10.1002/pssb.200301569.

15. Jump up^ Bridgman, P. W. (1914-07-01). "TWO NEW MODIFICATIONS OF PHOSPHORUS". Journal of the American Chemical Society. 36 (7): 1344–1363. doi:10.1021/ja02184a002. ISSN 0002-7863.

16. Jump up^ Lange, Stefan; Schmidt, Peer; Nilges, Tom (2007). "Au3SnP7@Black Phosphorus: An Easy Access to Black Phosphorus". Inorganic Chemistry. 46 (10): 4028–35. doi:10.1021/ic062192q. PMID 17439206.

17. Jump up^ Kang, J.; Ke, M.; Hu, Y. "Ionic Intercalation in Two-Dimensional van der Waals Materials: In Situ Characterization and Electrochemical Control of the Anisotropic Thermal Conductivity of Black Phosphorus". Nano Letters. 17: 1431. Bibcode:2017NanoL..17.1431K. doi:10.1021/acs.nanolett.6b04385.

18. Jump up^ Smith, B.; Vermeersch, B.; Carrete, J.; Ou, E.; Kim, J.; Li, S. "Temperature and Thickness Dependences of the Anisotropic In-Plane Thermal Conductivity of Black Phosphorus". Adv Mater. 29: 1603756.

19. Jump up^ Liu, Xiaolong D.; Wood, Joshua D.; Chen, Kan-Sheng; Cho, EunKyung; Hersam, Mark C. (9 February 2015). "In Situ Thermal Decomposition of Exfoliated Two-Dimensional Black Phosphorus". Journal of Physical Chemistry Letters. 6: 773–778. doi:10.1021/acs.jpclett.5b00043.

20. Jump up^ Wood, Joshua D.; Wells, Spencer A.; Jariwala, Deep; Chen, Kan-Sheng; Cho, EunKyung; Sangwan, Vinod K.; Liu, Xiaolong; Lauhon, Lincoln J.; Marks, Tobin J.; Hersam, Mark C. (7 November 2014). "Effective Passivation of Exfoliated Black Phosphorus Transistors against Ambient Degradation". Nano Letters. 14 (12): 6964–6970. arXiv:1411.2055 . Bibcode:2014NanoL..14.6964W. doi:10.1021/nl5032293. PMID 25380142.

21. Jump up^ Wu, Ryan J.; Topsakal, Mehmet; Low, Tony; Robbins, Matthew C.; Haratipour, Nazila; Jeong, Jong Seok; Wentzcovitch, Renata M.; Koester, Steven J.; Mkhoyan, K. Andre (2015-11-01). "Atomic and electronic structure of exfoliated black phosphorus". Journal of Vacuum Science & Technology A. 33 (6): 060604. doi:10.1116/1.4926753. ISSN 0734-2101.

22. Jump up^ Piro, Na; Figueroa, Js; Mckellar, Jt; Cummins, Cc (2006). "Triple-bond reactivity of diphosphorus molecules". Science. 313 (5791): 1276–

9. Bibcode:2006Sci...313.1276P. doi:10.1126/science.1129630. PMID 16946068.

23. ^ Jump up to:a b Pfitzner, A; Bräu, Mf; Zweck, J; Brunklaus, G; Eckert, H (Aug 2004). "Phosphorus nanorods – two allotropic modifications of a long-known element". Angewandte Chemie International Edition in English. 43 (32): 4228–31. doi:10.1002/anie.200460244. PMID 15307095.

24. Jump up^ A. Holleman; N. Wiberg (1985). "XV 2.1.3". Lehrbuch der Anorganischen Chemie (33 ed.). de Gruyter. ISBN 3-11-012641-9.

25. Jump up^ Berger, L. I. (1996). Semiconductor materials. CRC Press. p. 84. ISBN 0-8493-8912-7.

External links[edit] White phosphorus

White Phophorus at The Periodic Table of Videos (University of Nottingham)

More about White Phosphorus (and phosphorus pentoxide) at The Periodic Table of Videos (University of Nottingham)

Categories:

Allotropy

Phosphorus

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Languages

Español Français

Italiano Српски / srpski

Srpskohrvatski / српскохрватски

தமிழ்

中文

Edit links

This page was last edited on 31 January 2018, at 03:09.

Text is available under the Creative Commons Attribution-ShareAlike License; additional

terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy.

Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit

organization.

organization.