Decoupling transformation calculations of dynamical and vacancy-induced properties in FCC nickel metal

Abstract

In conjunction with the Kanzaki's lattice statics method, an alternative lattice dynamical model called decoupling transformation is proposed to calculate the vacancy-induced properties in FCC nickel metal. This approach has the advantage over the traditional least squares fit approach in the way that all model parameters are linearly independent and so it can avoid the problem of non-uniqueness in dynamical model parameters when interactions with more distant atoms are taken into account by fitting to the experimental phonon frequencies only. Numerical results on the lattice dynamical properties such as phonon dispersion curves and interatomic interaction force constants and the vacancy induced properties such as the atomic displacements, lattice relaxation energy, divacancy interaction energy and relaxation volume are obtained for nickel and are compared with previous calculations. It is found that the interatomic interactions up to fourth nearest neighbours are already good enough for describing both the lattice vibrational and vacancy induced properties of nickel.