Rh 3B 2−x, new structure type of binary borides with triclinic symmetry

Abstract

New binary compound Rh 3B 2− x , x = 0.167 crystallizing with its own structure type has been observed from the as cast alloys. The compound has a limited thermal stability range: it was found to decompose after annealing at 800 °C for 20 days. The crystal structure was investigated by X-ray diffraction from two single crystals using different techniques: CAD-4 automatic diffractometer, a = 5.470 (2), b = 6.816 (3), c = 9.068 (4), α = 110.74 (3), β = 94.81 (3), γ = 90.44 (2), 107 refined parameters, R 1 = 0.0418 , w R 2 = 0.1087 for 1223 reflections with I>2 σ( I o), and BRUKER SMART AXS, a = 5.483 ( 4 ) , b = 6.818 (6), c = 9.072 (7), a = 110.78 (1), b = 94.73 (1), g = 90.46 (1), 107 refined parameters, R 1 = 0.0401 , w R 2 = 0.0959 for 943 reflections with I > 2 σ ( I o ) . The Rh 3B 2− x , structure (space group P 1 ¯ , Pearson symbol aP 30 - 1 ) is the first representative of structures with triclinic symmetry among binary borides and contains three different types of boron-boron aggregation: isolated boron atoms, B–B pairs and B 6 chain fragments.