Interatomic forces in Pnma, Immm, P4/mbm and I4/mcm phase of R 2BaMO5(R= yttrium or lanthanides; M= Ni, Cu or Zn)

Abstract

The lattice dynamics of the stoichiometry R2BaMO5(R= lanthanides or yttrium; M= Ni, Cu or Zn) in its I4/mcm phase has been investigated. A short-range force constant model (SRFCM) has been applied to study the Raman and the infrared wavenumbers in Nd2BaZnO5 in its tetragonal phase of space group I4/mcm. Calculations of zone centre phonons are made with five stretching and five bending force constants. The Wilson-GF matrix method is used on the basis of Cartesian coordinate system. All the Raman and infrared values are then assigned to their corresponding modes on the basis of group theoretical analysis. The calculated Raman and infrared modes exhibit good agreement with the observed values. The potential energy distribution has been calculated for all the significant interactions. The calculated interatomic interactions are then compared with earlier calculations in the orthorhombic Pnma and Immm and tetragonal P4/mbm phases of the R 2BaMO5 series in order to understand the phase transformation and the physicochemical properties of the materials related to superconductors. © 2007 IOP Publishing Ltd.