VIBRATIONAL PROPERTIES AND ATOMIC DEBYE TEMPERATURES FOR LA2CUO4 FROM NEUTRON POWDER DIFFRACTION

Neutron powder diffraction data taken at five different temperatures have been used to determined both isotropic and anisotropic thermal parameters for atoms in La2CuO4. A fit of these parameters to a Debye-Waller model in turn yields the corresponding isotropic and anisotropic atomic Debye temperatures. The elastic properties of the atoms in these crystals are discussed in the context of the results from specific heat measurements, neutron resonance Doppler broadening studies of atomic Debye temperatures, inelastic neutron scattering studies of phonon densities of states and phonon dispersion curves, observed structural instabilities or anomalies associated with superconductivity at high temperatures, and results from lattice dynamical calculations.