Molecular Dynamics Simulations of Picotube PeapodsN. Rosenkranz and C. Thomsen

Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstraße 36, 10623 Berlin, Germany

References

[1] R. Herges, Nachrichten aus der Chemie, , 962 (2007).[2] S. Kammermeier et al., Angew. Chem. Int. Ed. Eng. 2669 (1996).[3] M. Machón et al., Phys. Rev. B , 155 402 (2005).[4] M. Field, J. Chem. Theory Comput. , 1151 (2008).[5] http://www.pdynamo.org

55

35,

72

4

Motivation

Carbon picotubes are a promising starting point for the specificsynthesis of nanotubes. One potentially useful configurationevolves from inserting picotubes into a nanotube. In this contextthe interaction between nanotubes and picotubes is of partic-ular interest.

1

Simulations

We place three Tetramer picotubes in a (9,9) nanotube.

Temperatures between 100 K and 3000 K are simulated.

All calculations are performed with the moleclular dynamicspackage , using the semiempirical quantumchemical model for the energy calculations. Structuralstudies of picotubes show an excellent agreement between ourresults and DFT calculations.

2,3

4,5pdynamo

AM1

ni-ro@gmx.de Kirchberg, March 2009

Outlook

Find suitable conditions for the synthesis of along inner nanotube.

Study the conditions for the transport of pico-tubes through the nanotube.

We observe three effects

T = 600 K

7.4 meVħw »

At 2500 K the open picotube transforms to aclosed configuration, e.g. a very short (4,4)nanotube.

When heated to 600 K the molecules perform an inverselyphased rotation.

At room temperature we observe a combination of the twomodes shown above.

Our studies clearly show a directional movement of the picotube molecules through thenanotube. The velocity increases with increasing temperature.in a range of 1000 - 2000 m/s

Oscillations of the picotubes inside thenanotube at up to 600 K

A structural reorganisation of the picotubestowards short nanotubes above 2000 K

A directional transport of the picotubemolecules starting at 800 K

Top and side view of a Tetramer picotubeas calculated with the code.This fully conjugated hydrocarbon whichstrongly resembles a short (4,4) nano-tube has been successfully synthesizedin 1996.

pdynamo4,5

2,3

T = 100 K

3.5 meV»ħw

All picotube molecules move in phase.

Initial configuration of the Tetramer picotubes in the nanotube. The type of nanotube is chosensuch that the distance between the nanotube wall and the hydrogen atoms at the wings of thetetramer slightly exceeds the carbon- hydrogen- bondlength.