Toward a total energy tight-binding Hamiltonian based on the linear-muffin-tin-orbital method

Abstract

We have investigated the accuracy of approximations involved in constructing a total energy tight-binding Hamiltonian for AuCu based on the linear-muffin-tin-orbital method in the atomic-sphere-approximation (LMTO-ASA). The approximations involved in constructing the tight-binding Hamiltonian are broken into four stages: (i) the use of the LMTO-ASA method, (ii) the use of only the first-order LMTO-ASA Hamiltonian, (iii) the use of non-self-consistent potential parameters, (iv) the use of a fit repulsive term. The equations of state are calculated for 11 different structures and compared at each stage of approximation. The results show that for AuCu the tight-binding Hamiltonian produces significant overbinding and errors in the equation of state.