Program for the calculation of a starting multicenter muffin-tin potential and the electron density

Abstract

Most of the quantum-chemical Xa methods are based on the muffin-tin (MT) approximation to the one-electron potential. In this case, the iteration process begins with the assignment of the radii of the MT spheres and the starting superposition of the electron densities of the atoms. For examp!e,:in the well-known SCF--X~SW program in [i] the calculation is carried out in two stages: in the first stage the wave functions of the free atoms are calculated according to a variant of the program in [2], and in the second stage, the molecular potential is constructed after the assignment of the radii of the MT spheres, and it is adjusted. Such a procedure is not very convenient, since the use of programs of the Herman-skillman type requires a large amount of input information, and the radii of the MT spheres are selected "manually." The program in [3], which is oriented to the SCF--Xa-SW program in [4], is another example, In our opinion, its shortcomings include the large volume of output data (the wave functions of the individual ions are printed out) and the absence of information which would permit the selection Of the MT radii on a well-established basis.