Effect of the coupling between electronic structure and crystalline structure on some properties of transition metals

The elastic constants, energetic stabilities and vacancy formation energies in transition metals are calculated within a Tight Binding model. In order to outline the effect of the electronic structure, these properties are represented as functions of band filling. The variation of the shear elastic constants of hexagonal close packed (HCP), body centered cubic (BCC) and face centered cubic (FCC) structures, is in contrast with the roughly parabolic behavior of bulk modulus. The general trends are in very good agreement with available experimental and 'ab initio' data. The vacancy formation energy in the BCC structure shows strong deviations from bell shape behavior with a maximum corresponding approximately to the band filling of group 6. This band filling effect contributes to the noticeable decrease of the self diffusion rate between group 4 and group 6. We demonstrate that the abrupt increase of the C' elastic constant, the NT1 (0.-1.1) phonon frequency, the energy differences between BCC and HCP and between FCC and HCP as well as the vacancy formation energy, that occurs when going from Zr to Mo, is related to the presence of a pseudo-gap in the density of states of the BCC structure. Using the recursion method, we show that the general trends of these properties are correctly reproduced when considering only a few moments of the density of states (about 6). On the other hand, details such as the elastic constant singularities, are displayed only with an exact calculation of the density of states. (Author). 173 refs., 84 figs., 5 tabs