title: Coupled-perturbed density-matrix functional theory equations. Application to static polarizabilities.
abstract: Starting from the variational equations for the natural occupation numbers and the recently proposed eigenequations for the natural spin-orbitals, we derive coupled-perturbed density-matrix equations that furnish a linear response of the one-electron reduced density matrix to a static perturbation when the total energy is a functional of the one-electron reduced density matrix. Cases when some occupation numbers achieve exactly 0 or 1 or when the total number of the particles in a system is not preserved are taken into consideration. The scheme is applied to computing static polarizabilities from two simple density-matrix functionals. The behavior of the functionals is erratic and they provide only little or no improvement over the coupled-perturbed Hartree-Fock results.
authors.affiliation: Afdeling Theoretische Chemie, Vrije Universiteit, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands. pernalk@univ.szczecin.pl
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Pernal
authors.forename: Evert Jan
authors.initials: EJ
authors.lastname: Baerends