THE HEAT OF TRANSPORT OF VACANCIES IN SOLID ARGON

Computer simulations of the motion of vacancies in a Lennard-Jones mod el of solid argon have been made by the molecular dynamics technique. The results have been used to evaluate and analyse the heat of transpo rt parameter Q(v) for vacancies in this substance. At a temperature o f 30 K it is found to be -12 kJ mol(-1). The theory of transport shows that there are three main contributions to this quantity coming from the fluxes of kinetic energy, potential energy and a virial of the for ces related to the local stress tenser. The main contribution to Q(v) is found to be that from the virial term. This explains why discussio ns that aim to relate the heat of transport to the corresponding entha lpy of activation (which is almost entirely potential energy) have not been successful.