Collection of Czechoslovak Chemical Communications - digital archive 

Abstract

The relative energies of a multitude of low-lying electronic states of Fe₂S^-/0/+ are determined by complete active space self-consistent field (CASSCF) calculations. The numerous states obtained are assigned to spin ladders. For selected states, dynamic correlation has been included by multireference configuration interaction (MRCI) and the structures of some high-spin states have been optimized by CASSCF/MRCI. Comparison is made with structures obtained by density-functional theoretical calculations. The ground states of Fe₂S^-/0/+ are ¹⁰B₂, ¹A₁ and ⁸A₂, respectively, and the total splittings of the lowest-energy spin ladders are about 0.18, 0.07 and 0.13 eV, respectively. The spin ladders of Fe₂S qualitatively reflect the picture of Heisenberg spin coupling. While both Fe₂S^- and Fe₂S⁺ show an Fe-Fe distance of about 270 pm, that of Fe₂S is about 100 pm longer. The calculated adiabatic electron affinity of Fe₂S is 1.2 eV and the ionization energy 6.6 eV. An interpretation of the observed photoelectron spectrum of Fe₂S^- is given.

Keywords: Iron sulfur clusters; Electronic structure; Spin ladders; Multireference configuration interaction; Complete active space SCF; Ab initio calculations.

References: 52 live references.