Abstract
Based on an analysis of phonon modes and the results of first-principles total-energy calculations for the cubic, tetragonal, and orthorhombic phases of VN, a possible mechanism of the cubic (space group ) to tetragonal (space group ) phase transition at 205 K is proposed. The mechanism suggests that spontaneous volume and shear strains, and , are induced indirectly by the collapse of the mode, indicating that the tetragonal phase exhibits improper ferroelasticity. The effect of nonmetal vacancy composition on phase transition is also discussed.
- Received 16 September 2008
DOI:https://doi.org/10.1103/PhysRevB.78.224113
©2008 American Physical Society