LATTICE-DYNAMICS STUDY OF TL2BA2CACU2O8 HIGH-TEMPERATURE SUPERCONDUCTOR

We present the frequencies of the Brillouin zone center phonon modes f or Tl2Ba2CaCu2O8, and give the phonon mode displacement patterns. The calculations are carried out in the framework of a simple force consta nt model, which includes first neighbor interactions and second neighb or interactions. The ten adjustable parameters are obtained by fitting the experimental data. Our calculated results are in good agreement w ith the experimental data available from Raman and infrared measuremen ts, and provide new assignments for some zone center phonon modes.