Exploiting the nearsightedness principle within the framework of the anti-Hermitian contracted Schrödinger equation

Abstract

This work exploits the Kohn nearsightedness principle in the algorithms arising from the anti-Hermitian contracted Schrödinger equation. The procedure provides the implementation of approximations yielding a considerable saving of computational costs in descriptions of N-electron molecular systems by means of that technique. We report energies, at correlated level, of linear hydrogen chains designed at different geometries, so that we can analyze the strength of the interactions between first-, second-, third-, fourth-, and so forth neighbor atoms. Using localized molecular orbital basis sets, we observe rapid decays in the values of the elements of the reduced-density-matrix cumulant matrices, beyond a cut-off radius, which justify the proposed approximations. The results, in terms of energies and reduced density matrices, have been compared with those obtained from the full configuration interaction method, showing the usefulness of the nearsightedness principle in this methodology.