FeNiP6 is Skutterudite-derived structured and crystallizes in the monoclinic C2/m space group. Fe(1) is bonded to two equivalent P(1), two equivalent P(3), and two equivalent P(4) atoms to form FeP6 octahedra that share corners with two equivalent Fe(1)P6 octahedra, corners with four equivalent Ni(1)P6 octahedra, and corners with four equivalent P(2)Ni2P2 tetrahedra. The corner-sharing octahedral tilt angles range from 59-60°. Ni(1) is bonded to two equivalent P(2), two equivalent P(3), and two equivalent P(4) atoms to form NiP6 octahedra that share corners with two equivalent Ni(1)P6 octahedra and corners with four equivalent Fe(1)P6 octahedra. The corner-sharing octahedral tilt angles range from 60-61°. There are four inequivalent P sites. In the first P site, P(1) is bonded in a distorted bent 120 degrees geometry to two equivalent Fe(1) and two equivalent P(2) atoms. In the second P site, P(2) is bonded to two equivalent Ni(1) and two equivalent P(1) atoms to form distorted PNi2P2 tetrahedra that share corners with four equivalent Fe(1)P6 octahedra, corners with two equivalent P(2)Ni2P2 tetrahedra, and  an edgeedge with one P(2)Ni2P2 tetrahedra. The corner-sharing octahedral tilt angles range from 68-71°. In the third P site, P(3) is bonded in a 4-coordinate geometry to one Fe(1), one Ni(1), and two equivalent P(3) atoms. In the fourth P site, P(4) is bonded in a 4-coordinate geometry to one Fe(1), one Ni(1), and two equivalent P(4) atoms.
FeNiP6 is Skutterudite-derived structured and crystallizes in the monoclinic C2/m space group. Fe(1) is bonded to two equivalent P(1), two equivalent P(3), and two equivalent P(4) atoms to form FeP6 octahedra that share corners with two equivalent Fe(1)P6 octahedra, corners with four equivalent Ni(1)P6 octahedra, and corners with four equivalent P(2)Ni2P2 tetrahedra. The corner-sharing octahedral tilt angles range from 59-60°. Both Fe(1)-P(1) bond lengths are 2.21 Å. Both Fe(1)-P(3) bond lengths are 2.19 Å. Both Fe(1)-P(4) bond lengths are 2.19 Å. Ni(1) is bonded to two equivalent P(2), two equivalent P(3), and two equivalent P(4) atoms to form NiP6 octahedra that share corners with two equivalent Ni(1)P6 octahedra and corners with four equivalent Fe(1)P6 octahedra. The corner-sharing octahedral tilt angles range from 60-61°. Both Ni(1)-P(2) bond lengths are 2.24 Å. Both Ni(1)-P(3) bond lengths are 2.27 Å. Both Ni(1)-P(4) bond lengths are 2.27 Å. There are four inequivalent P sites. In the first P site, P(1) is bonded in a distorted bent 120 degrees geometry to two equivalent Fe(1) and two equivalent P(2) atoms. There is one shorter (2.24 Å) and one longer (2.34 Å) P(1)-P(2) bond length. In the second P site, P(2) is bonded to two equivalent Ni(1) and two equivalent P(1) atoms to form distorted PNi2P2 tetrahedra that share corners with four equivalent Fe(1)P6 octahedra, corners with two equivalent P(2)Ni2P2 tetrahedra, and  an edgeedge with one P(2)Ni2P2 tetrahedra. The corner-sharing octahedral tilt angles range from 68-71°. In the third P site, P(3) is bonded in a 4-coordinate geometry to one Fe(1), one Ni(1), and two equivalent P(3) atoms. There is one shorter (2.24 Å) and one longer (2.33 Å) P(3)-P(3) bond length. In the fourth P site, P(4) is bonded in a 4-coordinate geometry to one Fe(1), one Ni(1), and two equivalent P(4) atoms. There is one shorter (2.23 Å) and one longer (2.33 Å) P(4)-P(4) bond length.