ELECTRONIC-STRUCTURE AND PHASE-STABILITY OF 3 SERIES OF B2 TI-TRANSITION-METAL COMPOUNDS

Self-consistent electronic structure calculations have been performed for the 12 B2 TiM compounds (M = Fe, Co, Ni, Cu; Ru, Ph, Pd, Ag; Os, I r, Pt, Au) using the linear muffin-tin orbital (LMTO) method. The calc ulated lattice constants and bulk moduli are in good agreement with me asurements. An analysis of the possible correlations between the insta bility of the B2 structure and the electronic structures of the 12 TiM compounds has been carried out. The sequence of the B2 phase instabil ities and the cubic --> orthorhombic (or monoclinic) --> orthorhombic (or monoclinic) --> tetragonal tendency in the three TiM series have b een discussed in terms of a band filling effect. The possible driving mechanisms of the structural phase transitions in the TiM series have been analysed based on the results of generalized susceptibility X(0)( q) calculations.