Electronic structure and phase stability of three series of B2 Ti-transition-metal compounds

Abstract

Self-consistent electronic structure calculations have been performed for the 12 B2 TiM compounds (M=Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Os, Ir, Pt, Au) using the linear muffin-tin orbital (LMTO) method. The calculated lattice constants and bulk moduli are in good agreement with measurements. An analysis of the possible correlations between the instability of the B2 structure and the electronic structures of the 12 TiM compounds has been carried out. The sequence of the B2 phase instabilities and the cubic to orthorhombic (or monoclinic) to orthorhombic (or monoclinic) to tetragonal tendency in the three TiM series have been 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 X0(q) calculations.

The investigation of electronic properties of Ti-based alloys

“…The consideration of the sub-antibonding peak which rises from the valley, where E F is located for alloys with N equal to 6.5 and 7 el shows that it is formed mainly by Me d-states which are as an admixture to Ti-states in this energy region. Thus, the present results and ones from [9] suggest a more complicated picture. The estimation of the charge in this region (from minimum up to E F ) gives 0.68 el.…”

“…There is no complete agreement between obtained band structure results for TiNi. ES of the monoclinic B19'-phase obtained by LMTO-ASA [7,9,10] and LAPW [8] method are at variance near the Fermi energy. It should be pointed out that the difference in the crystallographic data for B19'-phase [1][2][3][4] occurs.…”

“…The phase transitions in the alloys are proceeded by anomalies in various physical properties, which are summarized under the name of premartensitic phenomena. The TiNi crystal structure and properties have been studied in numerous experimental and theoretical works [1][2][3][4][5][6][7][8][9][10]. Several attempts have been made to explain MT in TiNi by specific features of the electronic structure (ES) of its parent B2-phase.…”

“…It should be pointed out that the difference in the crystallographic data for B19'-phase [1][2][3][4] occurs. The relationship between the instabilities of the B2-phases in the Ti-based alloys and the features of their electronic structure were discussed in the papers [6,[8][9][10][11]. The role of Ti d-states and their responsibility for the phase instability was stressed in [11].…”

Theoretical Investigations of Ti-Based Binary Shape Memory Alloys

“…The equilibrium lattice constants of the above mentioned systems in both phases are calculated. From Table 1, the theoretically obtained equilibrium lattice constants are underestimated compared to the experimental values [8], [a] Reference [9]; [b] Reference [10]; [c] Reference [11]. and this is partly ascribed to the local density approximation (LDA) used in the calculations.…”