All-electron pseudopotentials

We present an ab initio procedure for the construction of pseudopotentials accommodated to a crystal environment under study, which takes into account the response of the core charge density to the valence electrons of an ato m in a bond. Within pseudopotential methodology, core electrons are treated differently from valence electrons; however, the core electrons are consid ered as "frozen" in space and independent of the atom's valence electrons a fter they were relaxed and adapted to a crystal-valence charge density. In this way the frozen-core approximation is removed despite the fact that the frozen-core technique is still used and no all-electron solid-state calcul ation is required. Since the all-electron core-valence response is taken in to account properly, the treatment of nonlinear properties of exchange-corr elation functionals is naturally included and corrections using model core charges for nonlinear functionals are eliminated. Contrary to standard pseu dopotentials based on the atomic charge density of a free atom, the new all -electron pseudopotentials are functionals of the crystal charge density. C onsequently, the intuitive ad hoc choice of occupation numbers, which is ne cessary for the construction of pseudopotentials by existing methods, is av oided and energy windows for pseudopotentials are put at optimum positions. In this paper, core-level shifts were calculated within the pseudopotentia l framework. The results of test calculations for diamond, silicon, nonmagn etic fee P-Co, cubic TiC, and hexagonal TiS2 are presented. [S0163-1829(98) 05743-9].