Orthorhombic to monoclinic phase transition in NbNiTe2


The high-temperature structural phase transition of the potential topological material NbNiTe2 has been studied in detail. At high temperatures, the structure is centrosymmetric with orthorhombic space-group P2m2n21a(Pmna), and distorts at 373 K to a monoclinic structure with space-group P1121a(P1121/a). A small signature in specific heat and commensurate small release of entropy are observed at the phase transition. The low-temperature monoclinic structure retains its inversion center and the symmetries associated with the orthorhombic c axis. At high temperatures, NbNiTe2 shows phonon instabilities at Γ and X, which are removed by the structural phase transition. The electronic structure of NbNiTe2 is only slightly affected, indicating this ferroic phase transition is primarily due to steric effects.