Динамика решетки и нелинейный отклик ОЦК-титана на деформации при высокой температуре в методе ab initio молекулярной динамики

Abstract

The lattice dynamics and the response to deformations of the bcc titanium lattice at high temperatures are studied using the method of ab initio molecular dynamics. The results of calculation of phonon spectra using the harmonic Hamiltonian and the Hamiltonian containing third-order force constants are compared. It is shown that the lattice dynamics of bcc titanium cannot be correctly described without taking into account the anharmonic terms. Stress-strain curves are calculated for a given deformation scheme η1= η11= η, η6=2η12= η. For this deformation scheme, analytical expressions are given for the dependence of the nonzero components of the stress tensor on the magnitude of the deformation, taking into account the elastic constants up to the fourth order inclusive. All second-order elastic constants, three third-order elastic constants, and four fourth-order elastic constants of bcc titanium are calculated.