Materials Data on Ta2NiSe5 by Materials Project
Ta2NiSe5 crystallizes in the monoclinic C2/c space group. The structure is two-dimensional and consists of two Ta2NiSe5 sheets oriented in the (0, 1, 0) direction. Ta4+ is bonded to six Se2- atoms to form TaSe6 octahedra that share a cornercorner with one TaSe6 octahedra, edges with four equivalent TaSe6 octahedra, and edges with two equivalent NiSe4 tetrahedra. The corner-sharing octahedral tilt angles are 63°. There are a spread of Ta–Se bond distances ranging from 2.55–2.70 Å. Ni2+ is bonded to four Se2- atoms to form NiSe4 tetrahedra that share corners with two equivalent NiSe4 tetrahedra and edges with four equivalent TaSe6 octahedra. There are two shorter (2.36 Å) and two longer (2.39 Å) Ni–Se bond lengths. There are three inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a distorted T-shaped geometry to two equivalent Ta4+ and one Ni2+ atom. In the second Se2- site, Se2- is bonded in a 3-coordinate geometry to three equivalent Ta4+ atoms. In the third Se2- site, Se2- is bonded in a 4-coordinate geometry to two equivalent Ta4+ and two equivalent Ni2+ atoms.