INCABR3, AN ELECTRON ABSORBENT LAYERED MATERIAL CONTAINING UNIVALENT INDIUM

InCaBr3 is synthesized from InBr3 and elemental Ca at 450 degrees C, a nd its orthorhombic crystal structure (a = 425.49(1) pm, b = 1,407.81( 2) pm c = 1,089.24(1) pm; Cmcm; Z = 4), belonging to the filled PuBr3 type, has been determined by X-ray powder investigations. The layered structure contains corrugated sheets of corner- and edge-sharing octah edral [CaBr6](4-) units that alternate with layers of univalent indium ions, the latter being eightfold coordinated by bromine anions inside a bicapped trigonal prism. Ab initio valence charge density plots dis prove a possible directional ''lone-pair'' effect for In+ but suggest weakly attractive indium-indium interactions in those layers. Upon exp osure to an electron beam, InCaBr3 immediately exudes metallic indium as single crystals, leaving behind an amorphous material of approximat e composition CaBr3.