Whitfield Pamela S, Le Page Yvon, Grice Joel D, Stanley Chris J, Jones Gary C, Rumsey Michael S, Blake Chris, Roberts Andrew C, Stirling John A R, Carpenter Gordon J C
ICPET, National Research Council, Ottawa, Ontario, Canada.
Acta Crystallogr B. 2007 Jun;63(Pt 3):396-401. doi: 10.1107/S0108768107010130. Epub 2007 May 16.
The structure of a new mineral jadarite, LiNaSiB(3)O(7)(OH) (IMA mineral 2006-36), has been determined by simulated annealing and Rietveld refinement of laboratory X-ray powder diffraction data. The structure contains a layer of corner-sharing, tetrahedrally coordinated Li, Si and B forming an unbranched vierer single layer, which is decorated with triangular BO(3) groups. The Na ion is situated between the tetrahedral layers in a distorted octahedral site. As the very high boron content in this mineral makes obtaining neutron diffraction data very problematic, ab initio optimization using VASP was used to validate the structure and to better localize the H atom. The H atom is located on the apex of the triangular BO(3) group and is involved in a weak intralayer hydrogen bond. The final Rietveld refinement agrees with the ab initio optimization with regard to a hydrogen bond between the H atom and one of the tetrahedral corner O atoms. The refined structure seems to be of a remarkably high quality given the complexity of the structure, the high proportion of very light elements and the fact that it was determined from relatively low-resolution laboratory data over a limited 2theta range (10-90 degrees 2theta).
一种新矿物羟硼硅钠锂石（LiNaSiB₃O₇(OH)，IMA矿物2006 - 36）的结构已通过对实验室X射线粉末衍射数据进行模拟退火和Rietveld精修确定。该结构包含一层由角共享的、四面体配位的锂、硅和硼组成的无分支四元单层，其上装饰有三角形BO₃基团。钠离子位于四面体层之间的一个扭曲八面体位置。由于该矿物中极高的硼含量使得获取中子衍射数据非常困难，因此使用VASP进行从头算优化来验证结构并更好地确定氢原子的位置。氢原子位于三角形BO₃基团的顶点，并参与一个弱的层内氢键。最终的Rietveld精修在氢原子与一个四面体角氧原子之间的氢键方面与从头算优化结果一致。考虑到结构的复杂性、非常轻的元素的高比例以及它是从有限的2θ范围（10 - 90度2θ）内相对低分辨率的实验室数据确定的这一事实，精修后的结构似乎具有非常高的质量。
