APSe(6) (A = k, Rb, and Cs): Polymeric selenophosphates with reversible phase-change properties

Abstract

The ternary alkali selenophosphates KPSe6 and RbPSe6 crystallize in the polar orthorhombic space group Pca2(1) with a = 11.7764(17) Angstrom, b = 6.8580(10) Angstrom, c = 11.4596(16) Angstrom, and Z = 4 for RbPSe6. CsPSe6 crystallizes in the monoclinic space group P2/n with a = 6.877(3) Angstrom, b = 12.713(4) Angstrom, c = 11.242(4) Angstrom, beta = 92.735(7)degrees, and Z= 4. All compounds feature the one-dimensional infinite chain of [PSe2(Se)(4)(-)], where each P atom is connected with Se-4(2-) bridge. These compounds show reversible glass-crystal transition, and P-31 NMR data suggest that crystallization and infinite [PSe6-] chain formation are coupled processes.