A profound analysis of Rb-2[PH] and Cs-2[PH] and the role of [PH](2-) ions during temperature-induced solid-solid phase transitions

Abstract

The temperature-induced solid-solid transformation of Rb-2[PH] and Cs-2[PH] is characterized from both experiment and theory. Neutron diffraction, IR-spectroscopy and ab-initio molecular dynamics simulations reveal an asymmetric shift of the lattice constants at 80 K. The molecular mechanism of the structural transformation as identified from IR-spectroscopy and ab-initio molecular dynamics simulations is closely connected to the orientation of the [PH](2-) moieties which undergo a partial order-disorder phase transition.