Lattice vibrations in the HgBa2Ca2Cu3O8 high-temperature superconductor

We present the phonon density of states, the lattice specific heat C-v and the Debye temperature Theta(T) of the mercury based high-temperature superc onductor HgBa2Ca2Cu3O8 based on simple unscreened rigid ion model calculati ons. The obtained results show an overall consistent description of the lat tice vibrations in this compound. We could not compare our results with exp erimental measurements as these are nut available so far. However, we have compared the calculated values of C-v/T with measured C-p/T data and found a fair agreement between them within their uncertainties, We have also comp ared the phonon density of states of the Hg-1101 and Hg-1223 compounds and observed that there is a pronounced shift in the phonon density of states t owards the lower frequency side of the spectra with increasing number of Cu -O planes. We emphasize the desirability of neutron-scattering measurements to test our results, The results of calculations of mean square atomic vib rational amplitudes are also presented. (C) 1999 Elsevier Science B.V. All rights reserved.