The choice of the active space for multiconfigurational self-consistent-field in the description of the metalloproteines active sites

The article considers the electronic structure of oxidized state of the cluster [Fe(SCH 3) 4J which is an analog of the active site in rubredoxin proteins, in the framework of multiconfigurational self-consistent-field with complete and restriction active space. Our results show the applicability of the restriction active space to metal complex. The active space with the most accurate description of the static electron correlation is defined. The multireference character of the electronic wavefunctions is achieved by using two sets of molecular orbitals. The first set is five pure 3d-orbitals of Fe and the second three mixed molecular orbitals, which are linear combination of iron 3d-orbitals and sulfur p-orbitals. Based on RASSCF wavefunctions and this choice of the active space it is possible to describe binuclear metal complexes.