<i>Ab Initio</i> Simulation of Amorphous Graphite
Rajendra Thapa, Chinonso Ugwumadu, K. Nepal, Jason Trembly, D. A. Drabold
Abstract
An amorphous graphite material has been predicted from molecular dynamics simulation using ab initio methods. Carbon materials reveal a strong proclivity to convert into a ${\mathrm{sp}}^{2}$ network and then layer at temperatures near 3000 K within a density range of ca. $2.2--2.8\text{ }\text{ }\mathrm{g}/{\mathrm{cm}}^{3}$. Each layer of amorphous graphite is a monolayer of amorphous graphene including pentagons and heptagons in addition to hexagons, and the planes are separated by about $3.1\text{ }\text{ }\AA{}$. The layering transition has been studied using various structural and dynamical analyses. The transition is unique as one of partial ordering (long range order of planes and galleries, but topological disorder in the planes). The planes are quite flat, even though monolayer amorphous graphene puckers near pentagonal sites. Interplane cohesion is due partly to non-Van der Waals interactions. The structural disorder has been studied closely, especially the consequences of disorder to electronic transport. It is expected that the transition elucidated here may be salient to other layered materials.