title: Determination of Local Spins by Means of a Spin-Free Treatment.
abstract: This work describes a Mulliken-type partitioning of the expectation value of the spin-squared operator <Ŝ(2)> corresponding to an N-electron system. Our algorithms, which are based on a spin-free formulation, predict appropriate spins for the molecular fragments (at equilibrium geometries and at dissociation limits) and can be applied to any spin symmetry. Numerical determinations performed in selected closed- and open-shell systems at correlated level are reported. A comparison between these results and their counterpart ones arising from other alternative approaches is analyzed in detail.
authors.affiliation: Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and Instituto de Física de Buenos Aires , Consejo Nacional de Investigaciones Científicas y Técnicas, Ciudad Universitaria, 1428, Buenos Aires, Argentina.
authors.forename: Diego R
authors.initials: DR
authors.lastname: Alcoba
authors.affiliation: Departamento de Química Física, Facultad de Ciencia y Tecnología, Universidad del País Vasco , Apdo. 644 E-48080 Bilbao, Spain.
authors.forename: Alicia
authors.initials: A
authors.lastname: Torre
authors.affiliation: Departamento de Química Física, Facultad de Ciencia y Tecnología, Universidad del País Vasco , Apdo. 644 E-48080 Bilbao, Spain.
authors.forename: Luis
authors.initials: L
authors.lastname: Lain
authors.affiliation: Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and Instituto de Física de Buenos Aires , Consejo Nacional de Investigaciones Científicas y Técnicas, Ciudad Universitaria, 1428, Buenos Aires, Argentina.
authors.forename: Roberto C
authors.initials: RC
authors.lastname: Bochicchio