Elastic constants of tetrahedral amorphous carbon films:: the effect of intrinsic stresses

Atomic calculations, based on empirical potentials and the method of homogeneous deformation, are presented for the elastic properties of as-deposited amorphous carbon at 0 K. Several structural models of amorphous carbon generated by a realistic molecular-dynamics simulation of ion-beam deposition were studied. The models yield intrinsic compressive stresses of approximately 10 GPa. Here, we examine the dependence of the second-order elastic constants of amorphous carbon on the intrinsic stress. as well as on hydrostatic pressure. Different sets of elastic constants describing the behaviour of a solid under stress are considered. The non-Linear effects are shown to become appreciable at a pressure of 10 GPa, whereas the difference between the elastic constants in the equations of motion and the Lagrangian elastic constants is not large. (C) 2002 Elsevier Science B.V. All rights reserved.