THE B1-REVERSIBLE-ARROW-B2 PHASE-TRANSITION IN ALKALINE-EARTH OXIDES - A COMPARISON OF AB-INITIO HARTREE-FOCK AND DENSITY-FUNCTIONAL CALCULATIONS

Structural properties of the B-1 (NaCl-type) and B-2 (CsCl-type) phase s of alkaline-earth oxides and their phase transition have been invest igated with the periodic ab initio linear combination of atomic orbita ls method implemented in the CRYSTAL program. The geometries have been optimized and the bulk modulus evaluated. The calculations have been done at the Hartree-Fock (HF) and density functional theory (DFT) leve ls. In this last case, the exchange correlation potential correcting t he electronic density uses either one local or three non-local models. The comparison of the different approaches allows us to identify a tr end, in order to obtain results in better agreement with experiment.