Calculation of diatomic molecules by MOLCDO method

Calculations of excited states of the following three- and four-electron compounds: H2-, He2-, He2, Li2+2 are conducted using the earlier suggested basis of two-center functions and, therefore, high efficiency of approximation of frozen ion core and the method of non-orthogonal orbitals in these calculations is shown. Practical advisability of using approximation of the frozen mixed core is substantiated for four-electron systems