Nb3Se is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. There are three inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to eight Nb(1,1,1) and four equivalent Se(1) atoms to form distorted NbNb8Se4 cuboctahedra that share corners with four equivalent Se(1)Nb12 cuboctahedra; corners with fourteen Nb(1,1)Nb8Se4 cuboctahedra; edges with six equivalent Se(1)Nb12 cuboctahedra; edges with twelve Nb(1,1,1)Nb8Se4 cuboctahedra; faces with four equivalent Se(1)Nb12 cuboctahedra; and faces with sixteen Nb(1,1,1)Nb8Se4 cuboctahedra. In the second Nb site, Nb(1) is bonded to eight equivalent Nb(1) and four equivalent Se(1) atoms to form distorted NbNb8Se4 cuboctahedra that share corners with four equivalent Se(1)Nb12 cuboctahedra; corners with fourteen Nb(1,1)Nb8Se4 cuboctahedra; edges with six equivalent Se(1)Nb12 cuboctahedra; edges with twelve equivalent Nb(1)Nb8Se4 cuboctahedra; faces with four equivalent Se(1)Nb12 cuboctahedra; and faces with sixteen Nb(1,1,1)Nb8Se4 cuboctahedra. In the third Nb site, Nb(1) is bonded to eight equivalent Nb(1) and four equivalent Se(1) atoms to form distorted NbNb8Se4 cuboctahedra that share corners with four equivalent Se(1)Nb12 cuboctahedra; corners with fourteen Nb(1,1)Nb8Se4 cuboctahedra; edges with six equivalent Se(1)Nb12 cuboctahedra; edges with twelve equivalent Nb(1)Nb8Se4 cuboctahedra; faces with four equivalent Se(1)Nb12 cuboctahedra; and faces with sixteen Nb(1,1,1)Nb8Se4 cuboctahedra. Se(1) is bonded to twelve Nb(1,1,1) atoms to form SeNb12 cuboctahedra that share corners with six equivalent Se(1)Nb12 cuboctahedra; corners with twelve Nb(1,1)Nb8Se4 cuboctahedra; edges with eighteen Nb(1,1,1)Nb8Se4 cuboctahedra; faces with eight equivalent Se(1)Nb12 cuboctahedra; and faces with twelve Nb(1,1,1)Nb8Se4 cuboctahedra.
Nb3Se is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. There are three inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to eight Nb(1,1,1) and four equivalent Se(1) atoms to form distorted NbNb8Se4 cuboctahedra that share corners with four equivalent Se(1)Nb12 cuboctahedra; corners with fourteen Nb(1,1)Nb8Se4 cuboctahedra; edges with six equivalent Se(1)Nb12 cuboctahedra; edges with twelve Nb(1,1,1)Nb8Se4 cuboctahedra; faces with four equivalent Se(1)Nb12 cuboctahedra; and faces with sixteen Nb(1,1,1)Nb8Se4 cuboctahedra. There are a spread of Nb(1)-Nb(1,1,1) bond distances ranging from 2.78-2.99 Å. There are two shorter (2.88 Å) and two longer (3.01 Å) Nb(1)-Se(1) bond lengths. In the second Nb site, Nb(1) is bonded to eight equivalent Nb(1) and four equivalent Se(1) atoms to form distorted NbNb8Se4 cuboctahedra that share corners with four equivalent Se(1)Nb12 cuboctahedra; corners with fourteen Nb(1,1)Nb8Se4 cuboctahedra; edges with six equivalent Se(1)Nb12 cuboctahedra; edges with twelve equivalent Nb(1)Nb8Se4 cuboctahedra; faces with four equivalent Se(1)Nb12 cuboctahedra; and faces with sixteen Nb(1,1,1)Nb8Se4 cuboctahedra. There are two shorter (2.88 Å) and two longer (3.01 Å) Nb(1)-Se(1) bond lengths. In the third Nb site, Nb(1) is bonded to eight equivalent Nb(1) and four equivalent Se(1) atoms to form distorted NbNb8Se4 cuboctahedra that share corners with four equivalent Se(1)Nb12 cuboctahedra; corners with fourteen Nb(1,1)Nb8Se4 cuboctahedra; edges with six equivalent Se(1)Nb12 cuboctahedra; edges with twelve equivalent Nb(1)Nb8Se4 cuboctahedra; faces with four equivalent Se(1)Nb12 cuboctahedra; and faces with sixteen Nb(1,1,1)Nb8Se4 cuboctahedra. There are two shorter (2.88 Å) and two longer (3.01 Å) Nb(1)-Se(1) bond lengths. Se(1) is bonded to twelve Nb(1,1,1) atoms to form SeNb12 cuboctahedra that share corners with six equivalent Se(1)Nb12 cuboctahedra; corners with twelve Nb(1,1)Nb8Se4 cuboctahedra; edges with eighteen Nb(1,1,1)Nb8Se4 cuboctahedra; faces with eight equivalent Se(1)Nb12 cuboctahedra; and faces with twelve Nb(1,1,1)Nb8Se4 cuboctahedra.