Intrinsic stress and stiffness variations in amorphous carbon

We have studied the problem of intrinsic stress in tetrahedral amorphous carbon. Our methodology was based on the concept of atomic level stresses. These are extracted from the local energetics within the empirical potential approach. The finite temperature statistics of the system are described by Monte Carlo simulations. The universal finding of our investigations was that equilibrated, annealed films that relax the external constraints and pressure possess zero total intrinsic stress, but still contain a high fraction of sp(3) sites. This is in contrast to the case of non-equilibrium as-grown structures that are left intrinsically stressed by the deposition process. We also studied the variation of stiffness in the amorphous carbon network as a function of the average coordination. It was found that this variation deviates from a mean-field-like behavior. (C) 2001 Elsevier Science B.V. All rights reserved.