Electronic Structure Evolution during Martensitic Phase Transition in All-d-Metal Heusler Compounds: The Case of Pd_(2)MnTi

Taking Pd_(2)MnTi as a representative example,we systematically investigate and theoretically reveal the electronic structure evolution during martensitic phase transition in all-d-metal Heusler compounds.The calculation and theoretical analysis suggest that Pd_(2)MnTi is not stable in cubic structure and prone to transform to lowsymmetric tetragonal structure.By tetragonal deformation,the shrinkage of lattice parameters and the decrease of symmetry promote the electron accumulation between Pd and its first nearest neighboring Ti atom,resulting in the increasing covalent hybridization.The occurrence of pseudogap in density of states of tetragonal Pd_(2)MnTi near the Fermi level also verifies the enhancement of covalent bond.Comparatively,the stronger interatomic bond in tetragonal Pd_(2)MnTi,i.e.,covalent bond here,would strengthen interatomic coupling and consequently lower the energy of the material.By the martensitic phase transition,more stable states in energy are achieved.Thus,based on the analysis of electronic structure evolution,the nature of martensitic phase transition is a process wherein symmetry breaking weakens the original weak chemical bonds in high-symmetric parent phase and induces the strong chemical bond to lower the energy of the materials and to achieve a more stable state.This study could help to deepen the understanding of martensitic phase transition and the exploration of novel materials for potential technical applications.