Density functional and ab initio study of samarium dihalides, SmX₂ (X = I, Br, and Cl)

Quantum chemical calculations were performed to identify the closely lying septet electronic states of SmX2 (X = I, Br, and Cl) and their electronic structures were analysed. According to high-level ab initio calculations, the ground state of SmX2 (X = I, Br, and Cl) is the 7B1(2) state. The molecular structures of SmX2 (X = I, Br, and Cl) as optimised by B1B95 are very close to those obtained using coupled-cluster singles and doubles including perturbative corrections for the triple excitations (CCSD(T)). Since the electronic states of SmX2 (X = I, Br, and Cl) are quite close, the thermal average should be considered to compare the calculated results with the experimental ones. Descriptions of the molecular properties of SmX2 (X = I, Br, and Cl) are correlated to the ability to accurately describe the ionic bonding character of SmX2 (X = I, Br, and Cl).