Calculation of the transport matrix for the coupled diffusion of dopants and vacancies

A new approach is used for the calculation of transport coefficients for dopants and vacancies from atomic jump frequencies in the presence of dopant and vacancy gradients. The atomistic model involves seven different jump frequencies depending on the coordination numbers of the vacancy with respect to the dopant before and after the jump. With this approach, an interaction potential between the dopant and the point defect is taken into account with a maximum range up to the third coordination site. Results are shown for different types of attractive potentials with rectangular well shape and for Coulomb potentials. It is demonstrated that the fluxes of dopants and vacancies caused by a vacancy gradient may be in the same or opposite direction, depending only on the range of the potential.