Materials Data on U20Si16C3 by Materials Project

U20Si16C3 crystallizes in the hexagonal P6/mmm space group. The structure is three-dimensional. there are five inequivalent U3+ sites. In the first U3+ site, U3+ is bonded to twelve equivalent Si3- atoms to form face-sharing USi12 cuboctahedra. All U–Si bond lengths are 3.05 Å. In the second U3+ site, U3+ is bonded to twelve equivalent Si3- atoms to form face-sharing USi12 cuboctahedra. All U–Si bond lengths are 3.06 Å. In the third U3+ site, U3+ is bonded in a distorted single-bond geometry to four Si3- and one C4- atom. There are two shorter (2.85 Å) and two longer (3.01 Å) U–Si bond lengths. The U–C bond length is 2.35 Å. In the fourth U3+ site, U3+ is bonded in a 8-coordinate geometry to six Si3- and two equivalent C4- atoms. There are two shorter (2.89 Å) and four longer (2.94 Å) U–Si bond lengths. Both U–C bond lengths are 2.65 Å. In the fifth U3+ site, U3+ is bonded in a distorted hexagonal planar geometry to six Si3- atoms. There are two shorter (2.89 Å) and four longer (2.90 Å) U–Si bond lengths. There are two inequivalent Si3- sites. In the first Si3- site, Si3- is bonded in a 9-coordinate geometry to nine U3+ atoms. In the second Si3- site, Si3- is bonded in a 9-coordinate geometry to seven U3+ and two equivalent Si3- atoms. Both Si–Si bond lengths are 2.34 Å. C4- is bonded to six U3+ atoms to form corner-sharing CU6 octahedra. The corner-sharing octahedral tilt angles are 26°.

U₂₀Si₁₆C₃属六方晶系P6/mmm空间群，其晶体结构为三维结构。存在五个不等价的U³⁺位点。
在第一个U³⁺位点中，U³⁺与十二个等价的Si³⁻原子成键，形成面共享型USi₁₂立方八面体，所有U–Si键长均为3.05 Å。
在第二个U³⁺位点中，U³⁺与十二个等价的Si³⁻原子成键，形成面共享型USi₁₂立方八面体，所有U–Si键长均为3.06 Å。
在第三个U³⁺位点中，U³⁺以畸变单键配位几何与四个Si³⁻原子和一个C⁴⁻原子成键，存在两条较短的U–Si键（键长2.85 Å）与两条较长的U–Si键（键长3.01 Å），U–C键长为2.35 Å。
在第四个U³⁺位点中，U³⁺为八配位配位几何，与六个Si³⁻原子和两个等价的C⁴⁻原子成键，存在两条较短的U–Si键（键长2.89 Å）与四条较长的U–Si键（键长2.94 Å），两条U–C键长均为2.65 Å。
在第五个U³⁺位点中，U³⁺以畸变六方平面配位几何与六个Si³⁻原子成键，存在两条较短的U–Si键（键长2.89 Å）与四条较长的U–Si键（键长2.90 Å）。
存在两个不等价的Si³⁻位点。在第一个Si³⁻位点中，Si³⁻以九配位配位几何与九个U³⁺原子成键。在第二个Si³⁻位点中，Si³⁻以九配位配位几何与七个U³⁺原子和两个等价的Si³⁻原子成键，两条Si–Si键长均为2.34 Å。
C⁴⁻与六个U³⁺原子成键，形成共角型CU₆八面体，共角八面体的倾斜角为26°。