Operator spectrum transformation in Hartree–Fock and Kohn–Sham equations

The paper proposes a method for preliminary transformation of the spectrum of the equation operator both in the Hartree–Fock method and in density functional theory. This method allows to solve a partial eigenvalue problem instead of the complete one, while the eigenfunctions are ordered in a way convenient for calculation. The transformation makes an old idea of grid approximation of a solution competitive in terms of computational speed as compared to widely used approaches based on basis sets methods.