Ab initio investigation of pressure-induced structural transitions and electronic evolution of Th3N4

Abstract

ABSTRACTThe crystal structures, lattice dynamics, mechanical, electronic properties, and electron–phonon coupling of under environmental conditions and high pressures have been studied by merging first-principles calculations and particle-swarm optimization algorithm. Four structures are identified for , including the , , , and C2/m phases, in which the , , and C2/m phases are newly predicted. Their mechanical properties, including the Poisson's ratio σ, the elastic anisotropy factor , and the Pugh's ratio have been calculated and discussed. The results show that the , , and phases of behave ductile nature, while the C2/m phase behaves brittle nature. Among them, the phase of almost exhibits completely anisotropic nature. Besides, our electronic band structure calculations show that the pressure-induced semiconductor-metal transition occurs following the to phase transition. Further, the electron-phonon coupling of the phase has been analyzed. The results we obtained are of significance to further understand the physical essence of and its practical engineering applications.