The bain and orthorhombic paths of structural-phase transformations in a transition metal (V)

The energy of the Bain and orthorhombic paths of structural-phase transformations in a transition metal (V) under uniaxial deformation is studied by the ab-initio method. The orthorhombic path of transformation is refined in view of its symmetry. The softest branches of the phonon spectrum for the Bain path, responsible for the loss of structure stability, are found from the calculation of the phonon spectrum as a function of strain. The nature of the loss of stability is revealed, and the strain at which stability is lost under both tension and compression is evaluated. The most probable mechanisms determining the structure stability and the theoretical strength of the transition metal V are discussed. The results can relate to experimental situations of the deformation of small, defect-free regions, for example, in nanostructured materials, when surface layers are modified by plastic deformation, during nanoindentation, and during ultra-high plasticity of V-based alloys.