Effects of High Pressure on the Farhyphen;Infrared Spectra of Paraelectric KH2PO4and RbH2PO4

摘要

Using an opposedhyphen;anvilhyphen;type diamond cell, the infrared spectra of KH2PO4, RbH2PO4, and monoclinic RbD2PO4have been measured in the 100ndash;1400hyphen;cmminus;1region up to pressures of 60 kbar and at several temperatures. The roomhyphen;temperature spectrum of RbH2PO4demonstrates the existence of a new highhyphen;pressure phase where the PO4tetrahedra are distorted and the protons are ordered. This phase does not occur in monoclinic RbD2PO4. The results with KH2PO4are not as dramatic as RbH2PO4. The effects of high pressure in the 300ndash;600hyphen;cmminus;1region are similar to those obtained on cooling below the Curie temperaturelpar;Tcrpar;, and have been interpreted in terms of resonance interference between a multiphonon quasicontinuum and discrete states of the distorted PO4groups.