THE BEIJING 4-COMPONENT DENSITY-FUNCTIONAL PROGRAM PACKAGE (BDF) AND ITS APPLICATION TO EUO, EUS, YBO AND YBS

A four-component density functional program package (Beijing Density F unctional), suitable for the calculation of total-energy-related chemi cal properties of systems containing heavy atoms, was developed. The c ode is based on modern sophisticated exchange-col relation functionals and was applied to calculate the spectroscopic constants of the lanth anide diatomic molecules of EuO, EuS, YbO and YbS. It is suggested tha t the experimental bond lengths for EuS and YbS, derived from empirica l interpolations, need to be revised. Relativistic effects on the elec tronic structure are discussed and compared with results from previous work. The involvement of the lanthanide valence orbitals in chemical bending is investigated with a newly developed population and bonding analysis approach.