First principles simulation of phase transition in amorphous carbon

First principles mathematical modeling of phase transition in amorphous carbon is presented in the work. Supercomputer calculations, based on quantum mechanical Car–Parrinello molecular dynamics, are done (code CPMD). It is shown, that when temperature rises, graphite-like high conductive domains begin to dominate over diamond-like nonconducting domains. System energy has hysteresis character, when structure is heated and annealed. Sample atomic structure at given temperature might have different form depending on temperature change scenario, when given state is created. At given temperatures calculations of densities of states and Fermi energies are given, which show conductivity switching at certain temperature. Temperature percolation thresholds analysis, based on electronic density evolution of system, is given. It is shown, that switching from high resistive amorphous carbon structure to low resistive crystalline structure can be induced by thermal effects, which happen in experiments of nonvolatile memory, based on phase transition in amorphous carbon.