The structure of solid phosphorus pentabromide

Abstract

Abstract The Raman frequencies of solid phosphorus pentabromide, excited by the green and yellow mercury lines, are: 72(6), 140(14), 189(0 + ), 227(26), 367(2 − ) and 474(9). 72( v 2.3 ), 140( v 4,5,6 ), 227( v 1 ) and 474( v 7,8,9 ) are the fundamental vibrations of the nearly regular tetrahedron ‐formed by the group PBr 4 + , which together with Br − build up the lattice of solid PBr 5 . The force constants according to the Urey‐Bradley field are: K 1 = 2.19, K 2 = 0.18 and γ 3 = 0.028 all in 10 5 dynes/cm. The corresponding values for SiBr 4 , isoelectronic with PBr 4 + , are 1.99, 0.12 and 0.11 × 10 5 dynes/cm.