Materials Data on Er9B5S21 by Materials Project

Er9B5S21 crystallizes in the trigonal R3 space group. The structure is three-dimensional. there are six inequivalent Er3+ sites. In the first Er3+ site, Er3+ is bonded to seven S2- atoms to form distorted ErS7 pentagonal bipyramids that share corners with three ErS7 pentagonal bipyramids, corners with two BS4 tetrahedra, and an edgeedge with one BS4 tetrahedra. There are a spread of Er–S bond distances ranging from 2.69–2.88 Å. In the second Er3+ site, Er3+ is bonded in a 8-coordinate geometry to eight S2- atoms. There are a spread of Er–S bond distances ranging from 2.69–3.04 Å. In the third Er3+ site, Er3+ is bonded in a 7-coordinate geometry to seven S2- atoms. There are a spread of Er–S bond distances ranging from 2.62–2.87 Å. In the fourth Er3+ site, Er3+ is bonded in a 8-coordinate geometry to eight S2- atoms. There are a spread of Er–S bond distances ranging from 2.68–3.03 Å. In the fifth Er3+ site, Er3+ is bonded in a 7-coordinate geometry to seven S2- atoms. There are a spread of Er–S bond distances ranging from 2.64–2.88 Å. In the sixth Er3+ site, Er3+ is bonded to seven S2- atoms to form distorted ErS7 pentagonal bipyramids that share corners with three ErS7 pentagonal bipyramids, corners with two BS4 tetrahedra, and an edgeedge with one BS4 tetrahedra. There are a spread of Er–S bond distances ranging from 2.72–2.88 Å. There are six inequivalent B3+ sites. In the first B3+ site, B3+ is bonded to four S2- atoms to form BS4 tetrahedra that share corners with two ErS7 pentagonal bipyramids and an edgeedge with one ErS7 pentagonal bipyramid. There is two shorter (1.93 Å) and two longer (1.97 Å) B–S bond length. In the second B3+ site, B3+ is bonded to four S2- atoms to form BS4 tetrahedra that share corners with two ErS7 pentagonal bipyramids and an edgeedge with one ErS7 pentagonal bipyramid. There are a spread of B–S bond distances ranging from 1.93–1.96 Å. In the third B3+ site, B3+ is bonded in a trigonal planar geometry to three equivalent S2- atoms. All B–S bond lengths are 1.83 Å. In the fourth B3+ site, B3+ is bonded in a trigonal planar geometry to three equivalent S2- atoms. All B–S bond lengths are 1.83 Å. In the fifth B3+ site, B3+ is bonded in a trigonal planar geometry to three equivalent S2- atoms. All B–S bond lengths are 1.83 Å. In the sixth B3+ site, B3+ is bonded in a trigonal planar geometry to three equivalent S2- atoms. All B–S bond lengths are 1.83 Å. There are fourteen inequivalent S2- sites. In the first S2- site, S2- is bonded in a 4-coordinate geometry to three Er3+ and one B3+ atom. In the second S2- site, S2- is bonded in a 4-coordinate geometry to three Er3+ and one B3+ atom. In the third S2- site, S2- is bonded to four Er3+ atoms to form distorted corner-sharing SEr4 trigonal pyramids. In the fourth S2- site, S2- is bonded in a distorted see-saw-like geometry to three Er3+ and one B3+ atom. In the fifth S2- site, S2- is bonded in a 1-coordinate geometry to three Er3+ and one B3+ atom. In the sixth S2- site, S2- is bonded to four Er3+ atoms to form distorted SEr4 trigonal pyramids that share corners with three SEr4 trigonal pyramids and an edgeedge with one SEr3B trigonal pyramid. In the seventh S2- site, S2- is bonded in a distorted see-saw-like geometry to three Er3+ and one B3+ atom. In the eighth S2- site, S2- is bonded in a 1-coordinate geometry to three Er3+ and one B3+ atom. In the ninth S2- site, S2- is bonded in a 4-coordinate geometry to three Er3+ and one B3+ atom. In the tenth S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to three Er3+ and one B3+ atom. In the eleventh S2- site, S2- is bonded to three Er3+ and one B3+ atom to form a mixture of distorted edge and corner-sharing SEr3B trigonal pyramids. In the twelfth S2- site, S2- is bonded in a 4-coordinate geometry to three Er3+ and one B3+ atom. In the thirteenth S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to three Er3+ and one B3+ atom. In the fourteenth S2- site, S2- is bonded in a 4-coordinate geometry to three Er3+ and one B3+ atom.

Er₉B₅S₂₁晶体属于三方晶系（trigonal）R3空间群，为三维骨架结构。该体系包含6个非等价的铒离子（Er³+）配位位点：
在第1个Er³+位点中，Er³+与7个硫离子（S²-）配位，形成畸变的ErS₇五角双锥；该多面体通过顶点与3个ErS₇五角双锥、2个BS₄四面体共享，同时与1个BS₄四面体形成边共享，Er-S键长分布范围为2.69~2.88 Å。
在第2个Er³+位点中，Er³+采取8配位构型，与8个S²-离子配位，Er-S键长分布范围为2.69~3.04 Å。
在第3个Er³+位点中，Er³+采取7配位构型，与7个S²-离子配位，Er-S键长分布范围为2.62~2.87 Å。
在第4个Er³+位点中，Er³+采取8配位构型，与8个S²-离子配位，Er-S键长分布范围为2.68~3.03 Å。
在第5个Er³+位点中，Er³+采取7配位构型，与7个S²-离子配位，Er-S键长分布范围为2.64~2.88 Å。
在第6个Er³+位点中，Er³+与7个S²-离子配位，形成畸变的ErS₇五角双锥；该多面体通过顶点与3个ErS₇五角双锥、2个BS₄四面体共享，同时与1个BS₄四面体形成边共享，Er-S键长分布范围为2.72~2.88 Å。

该体系同时包含6个非等价的硼离子（B³+）配位位点：
在第1个B³+位点中，B³+与4个S²-离子配位，形成BS₄四面体；该四面体通过顶点与2个ErS₇五角双锥共享，同时与1个ErS₇五角双锥形成边共享，其B-S键存在两组长度：2个较短键长为1.93 Å，2个较长键长为1.97 Å。
在第2个B³+位点中，B³+与4个S²-离子配位，形成BS₄四面体；该四面体通过顶点与2个ErS₇五角双锥共享，同时与1个ErS₇五角双锥形成边共享，B-S键长分布范围为1.93~1.96 Å。
在第3至第6个B³+位点中，B³+均采取平面三角形配位构型，分别与3个等价的S²-离子配位，所有B-S键长均为1.83 Å。

该体系还包含14个非等价的硫离子（S²-）配位位点：
第1个S²-位点中，S²-为4配位，与3个Er³+和1个B³+离子成键；
第2个S²-位点中，S²-为4配位，与3个Er³+和1个B³+离子成键；
第3个S²-位点中，S²-与4个Er³+离子配位，形成畸变的共顶点SEr₄三角锥；
第4个S²-位点中，S²-采取畸变跷跷板构型，与3个Er³+和1个B³+离子成键；
第5个S²-位点中，S²-采取1配位构型，与3个Er³+和1个B³+离子成键；
第6个S²-位点中，S²-与4个Er³+离子配位，形成畸变的SEr₄三角锥；该三角锥通过顶点与3个SEr₄三角锥共享，同时与1个SEr₃B三角锥形成边共享；
第7个S²-位点中，S²-采取畸变跷跷板构型，与3个Er³+和1个B³+离子成键；
第8个S²-位点中，S²-采取1配位构型，与3个Er³+和1个B³+离子成键；
第9个S²-位点中，S²-为4配位，与3个Er³+和1个B³+离子成键；
第10个S²-位点中，S²-采取畸变矩形跷跷板构型，与3个Er³+和1个B³+离子成键；
第11个S²-位点中，S²-与3个Er³+和1个B³+离子配位，形成兼具畸变边共享与顶点共享特征的SEr₃B三角锥；
第12个S²-位点中，S²-为4配位，与3个Er³+和1个B³+离子成键；
第13个S²-位点中，S²-采取畸变矩形跷跷板构型，与3个Er³+和1个B³+离子成键；
第14个S²-位点中，S²-为4配位，与3个Er³+和1个B³+离子成键。