Ground state calculations of dihyphen;pgr;hyphen;cyclooctatetraene cerium

摘要

Quantum chemical calculations are presented which predict that in the ground state of dihyphen;pgr;hyphen;cyclooctatetraene cerium (cerocene) the Ce ion is almost entirely in a 4f1configuration corresponding to Ce3oplus;(C8H1.5squflg;8)2. The 4felectron forms with an electron of the ligande2uhighesthyphen;occupied molecular orbital a 4f1e32usinglet in close analogy to a Kondo ion in a metal. Due to coupling of the 4f1e32uwith the 4f0e42uconfiguration, the latter corresponding to Ce4oplus;(C8H2le;8)2, the splitting between the ground state singlet and the first excited triplet is of the order 0.5 eV. The selfhyphen;consistenthyphen;field and multiconfiguration selfhyphen;consistenthyphen;field parts of the calculations are done by employing recently developed pseudopotentials for cerium using basis sets of up to 626 basis functions. The correlation energy is accounted for by means of various correlationhyphen;energy density functionals and also by limited coupled electronhyphen;pair approximation calculations. Similar results are found in both cases.