Electronic, Vibrational and Thermal Properties of α and β Titanium

Abstract

Titanium and titanium-based alloys are widely used for various technological applications in the aerospace, automotive, and shipbuilding industries because of their good strength-to-weight ratio and good combination of mechanical properties. To understand the fundamental properties of titanium, as well as phase transformations, it is necessary to study the electronic and phonon structure of its main phases. Although such studies have been intensively carried out since the middle of the last century, theoretical studies of the phonon system and properties based on it remain rare. The atomic and electronic structures of α and β titanium are calculated by the projector augmented-wave method within the electron density functional theory. The analysis of the electron energy spectrum and the densities of electronic states is carried out. Using the harmonic approximation and the finite displacement method, the phonon spectrum and a number of related thermodynamic characteristics are calculated. The features of the phonon subsystem of β-Ti, which indicate its dynamic instability, are discussed. The calculation of the vibrational entropy and enthalpy, as well as the lattice heat capacity, showed satisfactory agreement with the experiment. In general, the approach used can be applied to analyze the forming phases of doped titanium.