Phase states in amorphous carbon

Abstract

Amorphous carbon (a-C) formed under energetic atom deposition and by cooling of a melt by MD simulations in a wide $P,T$-range is investigated. Simulations of a-C formation with atomic beam deposition reveal a sharp GLC-to-DLC transition with $z=3.35 $. The average coordination number, $ z $, depends on the depositing atom energy. Voronoi polyhedra of the 3-coordinated atoms changes dramatically in the vicinity of the transition while for the 4-coordinated atoms they are changing a few. The elastic moduli along with densities of states of electrons and phonons in the GLC and DLC states are investigated. Changes of a-C with temperature and pressure evolution and GLC-DLC transformations are studied. The map of isoconfigurational states on the ($P,T$)-plane shows regions of GLC and DLC phases stability.