Orthorhombic to monoclinic phase transition in NbNiTe2

Abstract

The high-temperature structural phase transition of the potential topological material ${\mathrm{NbNiTe}}_{2}$ has been studied in detail. At high temperatures, the structure is centrosymmetric with orthorhombic space-group $P\frac{2}{m}\frac{2}{n}\frac{{2}_{1}}{a}(Pmna)$, and distorts at 373 K to a monoclinic structure with space-group $P11\frac{{2}_{1}}{a}(P{112}_{1}/a)$. 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, ${\mathrm{NbNiTe}}_{2}$ shows phonon instabilities at $\mathrm{\ensuremath{\Gamma}}$ and $X$, which are removed by the structural phase transition. The electronic structure of ${\mathrm{NbNiTe}}_{2}$ is only slightly affected, indicating this ferroic phase transition is primarily due to steric effects.