Electronic and structural properties of CaH2:: a pseudopotential study

The Hartee-Fock ab initio method is used to evaluate some properties of CaH2 solid system. The all electrons (5-111G) basis set is used to describe the hydrogen atom. For the calcium atom, the HAWLC pseudopotential is employed to describe the internal electrons. The two electrons of valence are described using s or sp orbitals. The effect of the d(Ca) orbital on the structural, electronic and dynamic properties is discussed. For all the basis sets used in this work, CaH2 is a strongly ionic insulator. The valence band is primarily constituted by the 3s(H) orbital. The 2s(H) and Is(H) orbitals participate, with a nonnegligible manner, to its formation. The conduction band is formed by 4s(Ca) (or 4sp(Ca)), 2p(H) and 2s(H) orbitals. The addition of the d(Ca) orbital has a remarkable effect on this band. Good linear relationships are established between the elastic constants, calculated with pseudopotential basis sets, and their equivalents calculated with all electrons basis sets. (C) 2000 Elsevier Science B.V. All rights reserved.