TOWARD A TOTAL-ENERGY TIGHT-BINDING HAMILTONIAN BASED ON THE LINEAR-MUFFIN-TIN-ORBITAL METHOD

We have investigated the accuracy of approximations involved in constr ucting 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-bindi ng Hamiltonian are broken into four stages: (i) the use of the LMTO-AS A method, (ii) the use of only the first-order LMTO-ASA Hamiltonian, ( iii) the, use of non-serf-consistent potential parameters, (iv) the us e of a fit repulsive term, The equations of state are calculated for 1 1 different structures and compared at each stage of approximation, Th e: results show that for Au-Cu the tight-binding Hamiltonian produces significant overbinding and errors in the equation of state.