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 superconductor HgBa2Ca2Cu3O8 based on simple unscreened rigid ion model calculations. The obtained results show an overall consistent description of the lattice vibrations in this compound. We could not compare our results with experimental 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 compared 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 towards 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 vibrational amplitudes are also presented. (C) 1999 Elsevier Science B.V. All rights reserved.