The crystal structure of rhenium diboride

Abstract

The crystal structure of ReB 2 has been determined from powder data. The unit cell is hexagonal; a=2.900 and c=7.478 A; there are two ReB 2 units per unit cell. The structure may be described in terms of alternating layers of rhenium and boron atoms; the former are planar, the latter are puckered. The two boron atoms show up clearly in difference maps (@z, 2x, Zobs. --@z, 2x, ZRe)" B-B bond lengths are 1.82 ~; shortest Re-B distance are 2.23 and 2.26 A. The transition metals react with boron to form a large number of simple binary phases. The diboride phases have been most extensively studied, mainly because of their simple crystal structures and interest-ing physical and chemical properties. Most of the transition metals form a series of iso-morphous diborides (Post, Glaser & Moskowitz, 1954); the unit cells are hexagonal, the space group is P6/mmm and there is one formula weight per unit cell,