New high pressure phase and local distortion of PO4 in RbH2PO4

Abstract High pressure Raman scattering experiments and X-ray diffraction measurements of RbH 2 PO 4 have been performed with a diamond anvil cell. The v 4 internal mode of PO 4 tetrahedron in X ( ZZ ) − X Raman scattering spectra disappears above 2.5 GPa. Above 4.5 GPa a new high pressure phase appears where both v 3 and v 4 modes reappear and the v 4 modes split into two peaks. This high pressure phase was also confirmed by X-ray diffraction.