Materials Data on Nd2MgSe4 by Materials Project

MgNd2Se4 is Spinel-like structured and crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Mg2+ is bonded to four Se2- atoms to form MgSe4 tetrahedra that share corners with six NdSe6 octahedra and edges with three NdSe6 octahedra. The corner-sharing octahedra tilt angles range from 59–64°. There are a spread of Mg–Se bond distances ranging from 2.55–2.62 Å. There are two inequivalent Nd3+ sites. In the first Nd3+ site, Nd3+ is bonded to six Se2- atoms to form NdSe6 octahedra that share corners with four equivalent NdSe6 octahedra, corners with two equivalent MgSe4 tetrahedra, edges with four NdSe6 octahedra, and edges with two equivalent MgSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 51–56°. There are a spread of Nd–Se bond distances ranging from 2.95–3.01 Å. In the second Nd3+ site, Nd3+ is bonded to six Se2- atoms to form NdSe6 octahedra that share corners with eight NdSe6 octahedra, corners with four equivalent MgSe4 tetrahedra, edges with two equivalent NdSe6 octahedra, and an edgeedge with one MgSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 47–56°. There are a spread of Nd–Se bond distances ranging from 2.94–3.02 Å. There are three inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Nd3+ atoms. In the second Se2- site, Se2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Nd3+ atoms. In the third Se2- site, Se2- is bonded to one Mg2+ and three Nd3+ atoms to form distorted corner-sharing SeNd3Mg trigonal pyramids.

MgNd₂Se₄ 具有类尖晶石结构（Spinel-like structure），结晶于正交晶系（orthorhombic）的Pnma空间群。该结构为三维框架结构。Mg²+与四个Se²-配位形成MgSe₄四面体（tetrahedra），该四面体与六个NdSe₆八面体（octahedra）共享顶点，同时与三个NdSe₆八面体共享棱边。共享顶点的八面体倾斜角范围为59°~64°。Mg-Se键的键长分布在2.55~2.62 Å之间。

存在两个不等价的Nd³+位点：在第一个Nd³+位点中，Nd³+与六个Se²-配位形成NdSe₆八面体，该八面体与四个等价的NdSe₆八面体共享顶点，与两个等价的MgSe₄四面体共享顶点，同时与四个NdSe₆八面体共享棱边，与两个等价的MgSe₄四面体共享棱边。共享顶点的八面体倾斜角范围为51°~56°。Nd-Se键的键长分布在2.95~3.01 Å之间。

在第二个Nd³+位点中，Nd³+与六个Se²-配位形成NdSe₆八面体，该八面体与八个NdSe₆八面体共享顶点，与四个等价的MgSe₄四面体共享顶点，同时与两个等价的NdSe₆八面体共享棱边，与一个MgSe₄四面体共享棱边。共享顶点的八面体倾斜角范围为47°~56°。Nd-Se键的键长分布在2.94~3.02 Å之间。

存在三个不等价的Se²-位点：在第一个Se²-位点中，Se²-以矩形跷跷板状配位几何（rectangular see-saw-like geometry）与一个Mg²+和三个Nd³+原子配位。在第二个Se²-位点中，Se²-以矩形跷跷板状配位几何与一个Mg²+和三个Nd³+原子配位。在第三个Se²-位点中，Se²-与一个Mg²+和三个Nd³+原子配位，形成畸变的、共享顶点的SeNd₃Mg三角锥（trigonal pyramids）结构。