关键词: 密度矩阵, 局域活性泛函空间, 程序

Abstract: A method is proposed to construct a localized active functional space from the density matrix of a large system. The large system is partitioned into central and surrounding areas. The active functional space is mainly localized on the central area. It contains all basis functions centered at the central area and all the orbitals which consist of the basis functions localized in the surrounding area and interact with the basis functions in the central area to a certain extent. An integral number of electrons are involved in the localized active functional space which can be considered as a relatively independent subsystem in the large system and for which formally isolated quantum chemical calculations can be performed. The related program has been coded and is checked through calculating the number of 4f electrons involved in the active functional space centered in the lanthanide atom of lanthanide trichloride and hydrated lanthanide ions.

Key words: density matrix, localized active functional space, program