Computer simulations were made of the motion of vacancies, in a Lennard-Jones model of the solid, by using a molecular dynamics technique. The results were used to evaluate and analyze the heat of transport for vacancies. It was found that, at a temperature of 30K, it was equal to -12kJ/mol. The theory of transport showed that there were 3 main contributions to this parameter. These arose from the fluxes of kinetic energy, potential energy and a virial of forces that were related to the local stress tensor. The main contribution to the heat of transport was found to be that which arose from the virial term. This explained why attempts to relate the heat of transport to the corresponding activation enthalpy (which was almost entirely potential energy) had not been successful.

C.Jones, P.J.Grout, A.B.Lidiard: Philosophical Magazine Letters, 1996, 74[3], 217-23