Calculation of the Raman frequency and the damping constant of a coupled mode in the ferroelectric and paraelectric phases in KH(2)PO(4)

KARACALİ H., Kiraci A., YURTSEVEN H. H.

PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, vol.247, no.4, pp.927-936, 2010 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 247 Issue: 4
  • Publication Date: 2010
  • Doi Number: 10.1002/pssb.200945181
  • Journal Name: PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.927-936
  • Keywords: Raman frequency, damping constant, KH(2)PO(4), lattice dynamics, TEMPERATURE-DEPENDENCE, HIGH-PRESSURE, AMMONIUM HALIDES, SOFT MODE, KDP, TRANSITIONS, CRYSTALS, SCATTERING, PHONONS, LAMBDA
  • Middle East Technical University Affiliated: Yes

Abstract

The Raman frequency of the coupled mode omega_ associated with the order parameter is calculated as a function of pressure from the mean field theory in the ferroelecric phase of KDP. Using the frequencies of the coupled mode, the pressure dependence of the damping constant Gamma_ is calculated by the proton spin lattice relaxation time and by the energy fluctuation of this mode of KDP in the ferroelectric (FE) phase. For the paraelectric (PE) phase, the Raman frequency of the coupled mode omega is calculated as a function of temperature at 6.54 kbar. The temperature dependence of the damping constant Gamma_ is performed only by the energy fluctuation of the coupled mode omega_ in the PE phase of KDP. The values of the activation energy U are extracted from the pressure and temperature dependence of the damping constant Gamma_ of this coupled mode omega_ for both FE and PE phase of KDP. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim