On the effect of quench rate on the structure of amorphous carbon

Abstract

We have simulated, via tight binding molecular dynamics (TBMD), the process of the quench from a melt of an atomic scale system of carbon. We have correlated the local properties of the resulting structure to the quench rate used to bring the liquid phase beyond the glass transition temperature. Results have been analyzed also in terms of the hamiltonian model used to describe the simulated system. In this respect, amorphous structures generated via tight binding and ab initio molecular dynamics have been compared. Results indicate that quench rates as slow as 1014 K/s produce the onset of an increasingly high fraction of threefold coordinated sites in the structure. Moreover, it has been put in evidence the tendency of the tight binding approach to favor threefold coordinated sites with respect to fourfold coordinated, even in the fast quench rates domain.