Ab initio structure determination of novel borate NaSrBO 3

Abstract

A novel orthoborate, NaSrBO 3, has been successfully synthesized by standard solid-state reaction, and the crystal structure has been determined from powder X-ray diffraction data. It crystallizes in the monoclinic space group P 2 1 / c with lattice parameters: a = 5.3 2 4 4 6 ( 7 ) Å , b = 9.2 6 8 4 ( 1 ) Å , c = 6.0 6 6 8 3 ( 8 ) Å , β = 1 0 0.5 8 9 ( 1 ) ° . The fundamental building units are isolated BO 3 groups, which are parallelly distributed along two different directions. Because of the anisotropic polarizations of planar BO 3 groups, a considerable birefringence can be expected in it. The Na atoms are six-coordinated with O atoms to form octahedra, and the Sr atoms are nine-coordinated, forming tri-capped trigonal prisms. Those polyhedra connect with each other by bridging-oxygen atoms, forming infinite three-dimensional network, which indicates that the cleaving problem is expected to be overcome during the course of single-crystal growth. The infrared spectrum has been measured, and the result is consistent with the crystallographic study. Moreover, a comparison of the new structure type with the other known orthoborates is presented here.