Diamond and Related Materials, 4(4), 528-521 (1995)

Hypothetical C₁₀₀ molecule and the diamond-graphite interface: unstable and metastable states of carbon

C. D. Latham, M. I. Heggie

Scientific Computing Group, Department of Computer Science, University of Exeter, Exeter, EX4 4PT, UK

(Received 12th August 1994; accepted in final form 23rd November 1994)

Abstract

We summarise our ab initio calculations on diamond to date and their consequences for diamond film growth.  Local spin density calculations on 50 and 62 atom clusters have given good estimates for hydrogenation reactions including activation energies and surface reconstructions.  Larger calculations on the icosahedral, tetrahedrally bonded C₁₀₀ molecule reveal it should spontaneously decompose into two concentric fullerenes (C₂₀ and C₈₀).  It is possible that a similar mechanism might cause graphitisation at a diamond asperity if hydrogen were not present, at least where a twin boundary meets the surface.  On the other hand, the saturated, tetrahedrally-bonded C₁₀₀H₆₀ molecule was found to be stable, elegantly illustrating one of the much-discussed roles of hydrogen in diamond growth.

We have tested the graphite-diamond interface model of Lambrecht et al. (Nature 364 (1993) 607-610) and find the interface to be stable, but less so than their interatomic potential calculations suggested.  We find some evidence for bond reconstruction and basal dislocation formation.

Keywords: modelling, growth mechanisms, metastable carbon, interfaces

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