Stress tensor in the linearized augmented plane wave method

Abstract

In this paper we present a detailed derivation of the stress tensor for the nonrelativistic full potential linearized augmented plane wave (LAPW) method. The formalism has been implemented into the wien2k code and has been thoroughly tested for the equilibrium lattice parameters in various solids. Hydrostatic and nonhydrostatic conditions have been applied and the accuracy of individual stress components has been tested at finite strain. We also tested the convergence of the stress tensor with respect to the basis set and found it necessary to increase the basis set a bit as compared to total energy calculations. The effect of the tetrahedron and Fermi-Dirac (FD) methods on the calculated stress is studied for aluminum and found that the FD method improves the results. Finally, a brief comparison with previous attempts in the literature on this topic is given.