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Ni17(GeSe)4 crystallizes in the tetragonal P4mm space group. The structure is two-dimensional and consists of one Ni17(GeSe)4 sheet oriented in the (0, 0, 1) direction. there are twelve inequivalent Ni sites. In the first Ni site, Ni is bonded to eight Ni and four Ge atoms to form NiNi8Ge4 cuboctahedra that share corners with four equivalent NiNi8Ge4 cuboctahedra, edges with eight NiNi8Ge4 cuboctahedra, edges with eight GeNi12 cuboctahedra, faces with four GeNi12 cuboctahedra, and faces with twelve NiNi8Ge4 cuboctahedra. There are a spread of Ni–Ni bond distances ranging from 2.50–2.55 Å. There are two shorter (2.53 Å) and two longer (2.54 Å) Ni–Ge bond lengths. In the second Ni site, Ni is bonded to eight Ni and four Ge atoms to form NiNi8Ge4 cuboctahedra that share corners with four equivalent NiNi8Ge4 cuboctahedra, edges with eight NiNi8Ge4 cuboctahedra, edges with eight GeNi12 cuboctahedra, faces with four GeNi12 cuboctahedra, and faces with twelve NiNi8Ge4 cuboctahedra. There are four shorter (2.51 Å) and four longer (2.55 Å) Ni–Ni bond lengths. There are two shorter (2.54 Å) and two longer (2.55 Å) Ni–Ge bond lengths. In the third Ni site, Ni is bonded to eight Ni and four Ge atoms to form NiNi8Ge4 cuboctahedra that share corners with four equivalent NiNi8Ge4 cuboctahedra, edges with eight NiNi8Ge4 cuboctahedra, edges with eight GeNi12 cuboctahedra, faces with four GeNi12 cuboctahedra, and faces with twelve NiNi8Ge4 cuboctahedra. There are two shorter (2.50 Å) and two longer (2.51 Å) Ni–Ni bond lengths. There are two shorter (2.53 Å) and two longer (2.54 Å) Ni–Ge bond lengths. In the fourth Ni site, Ni is bonded in a 12-coordinate geometry to eight Ni, two equivalent Ge, and two equivalent Se atoms. There are a spread of Ni–Ni bond distances ranging from 2.53–2.64 Å. Both Ni–Ge bond lengths are 2.48 Å. Both Ni–Se bond lengths are 2.43 Å. In the fifth Ni site, Ni is bonded in a 2-coordinate geometry to two equivalent Ni, two equivalent Ge, and two equivalent Se atoms. Both Ni–Ni bond lengths are 2.54 Å. Both Ni–Ge bond lengths are 2.50 Å. Both Ni–Se bond lengths are 2.33 Å. In the sixth Ni site, Ni is bonded in a 2-coordinate geometry to two equivalent Ni, two equivalent Ge, and two equivalent Se atoms. Both Ni–Ni bond lengths are 2.54 Å. Both Ni–Ge bond lengths are 2.51 Å. Both Ni–Se bond lengths are 2.32 Å. In the seventh Ni site, Ni is bonded in a 2-coordinate geometry to two equivalent Ni, two equivalent Ge, and two equivalent Se atoms. Both Ni–Ni bond lengths are 2.53 Å. Both Ni–Ge bond lengths are 2.52 Å. Both Ni–Se bond lengths are 2.33 Å. In the eighth Ni site, Ni is bonded to eight Ni and four equivalent Ge atoms to form NiNi8Ge4 cuboctahedra that share corners with eight NiNi8Ge4 cuboctahedra, edges with four equivalent GeNi12 cuboctahedra, edges with eight NiNi8Ge4 cuboctahedra, edges with four equivalent NiNi4Se5 square pyramids, faces with four equivalent GeNi12 cuboctahedra, and faces with nine NiNi8Ge4 cuboctahedra. All Ni–Ge bond lengths are 2.55 Å. In the ninth Ni site, Ni is bonded to eight Ni and four equivalent Ge atoms to form NiNi8Ge4 cuboctahedra that share corners with eight NiNi8Ge4 cuboctahedra, edges with four equivalent GeNi12 cuboctahedra, edges with eight equivalent NiNi8Ge4 cuboctahedra, faces with four equivalent GeNi12 cuboctahedra, and faces with nine NiNi8Ge4 cuboctahedra. All Ni–Ge bond lengths are 2.55 Å. In the tenth Ni site, Ni is bonded to eight Ni and four equivalent Ge atoms to form NiNi8Ge4 cuboctahedra that share corners with eight NiNi8Ge4 cuboctahedra, edges with four equivalent GeNi12 cuboctahedra, edges with eight equivalent NiNi8Ge4 cuboctahedra, faces with four equivalent GeNi12 cuboctahedra, and faces with nine NiNi8Ge4 cuboctahedra. All Ni–Ge bond lengths are 2.55 Å. In the eleventh Ni site, Ni is bonded to eight Ni and four equivalent Ge atoms to form NiNi8Ge4 cuboctahedra that share corners with eight NiNi8Ge4 cuboctahedra, edges with four equivalent GeNi12 cuboctahedra, edges with eight NiNi8Ge4 cuboctahedra, faces with four equivalent GeNi12 cuboctahedra, and faces with nine NiNi8Ge4 cuboctahedra. All Ni–Ge bond lengths are 2.55 Å. In the twelfth Ni site, Ni is bonded to four equivalent Ni and five Se atoms to form distorted NiNi4Se5 square pyramids that share corners with four equivalent GeNi12 cuboctahedra, corners with four equivalent NiNi4Se5 square pyramids, edges with four equivalent NiNi8Ge4 cuboctahedra, a faceface with one GeNi12 cuboctahedra, and faces with four equivalent NiNi4Se5 square pyramids. There are one shorter (2.28 Å) and four longer (2.56 Å) Ni–Se bond lengths. There are four inequivalent Ge sites. In the first Ge site, Ge is bonded to twelve Ni atoms to form GeNi12 cuboctahedra that share corners with eight GeNi12 cuboctahedra, corners with four equivalent NiNi4Se5 square pyramids, edges with twelve NiNi8Ge4 cuboctahedra, faces with five GeNi12 cuboctahedra, faces with eight NiNi8Ge4 cuboctahedra, and a faceface with one NiNi4Se5 square pyramid. In the second Ge site, Ge is bonded to twelve Ni atoms to form GeNi12 cuboctahedra that share corners with eight GeNi12 cuboctahedra, edges with twelve NiNi8Ge4 cuboctahedra, faces with five GeNi12 cuboctahedra, and faces with eight NiNi8Ge4 cuboctahedra. In the third Ge site, Ge is bonded to twelve Ni atoms to form GeNi12 cuboctahedra that share corners with eight GeNi12 cuboctahedra, edges with twelve NiNi8Ge4 cuboctahedra, faces with five GeNi12 cuboctahedra, and faces with eight NiNi8Ge4 cuboctahedra. In the fourth Ge site, Ge is bonded to twelve Ni atoms to form GeNi12 cuboctahedra that share corners with eight GeNi12 cuboctahedra, edges with twelve NiNi8Ge4 cuboctahedra, faces with five GeNi12 cuboctahedra, and faces with eight NiNi8Ge4 cuboctahedra. There are four inequivalent Se sites. In the first Se site, Se is bonded in a 8-coordinate geometry to eight Ni atoms. In the second Se site, Se is bonded in a 4-coordinate geometry to four equivalent Ni atoms. In the third Se site, Se is bonded in a 5-coordinate geometry to five Ni atoms. In the fourth Se site, Se is bonded in a 4-coordinate geometry to four equivalent Ni atoms.

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