Refinement of the crystal structure of triclinic magnesium pyroborate

Abstract

The t riclinic m odification of M gzBz0 5 wa s classifi ed as a m ember of a n isostr uct ural seri es which also includes MnzBz0 5, F ezBz0 5, and C02Bz0 5 • Th e cr ystal st ru cture was re fi ned by the use of successive Fourier projectio ns and a least-squares refi nement program on a n electroni c compu ter. The structur e of MgzBzOs consists of B20 5-4 groups a nd MgH ions. E ach magnesium atom is s urr ounded octahedrally by six oxygen ato ms, forming an extended sheet of octahedra. The p yro borate gro ups share corn ers wit h octahedra in t he sheals a nd t h.us link t hem. E ach boron ato m is in planar triang ul a r coordi nation wit h t hree oxygen atoms. The pyroborate group h as t wo s uch t riangles with o ne shar ed oxygen. Th e a ngle between t he planes formed by t he t ria ngles is 16°. The ave rage boro n-to-oxyge n distance is 1. 38 A.