Rigid-ion model calculations of phonon dispersion relations, densities of states and partial densities of states of the highTc superconductor La2CuO4 and its isostructural compound La2NiO4 have been carried out both in the tetragonal and orthorhombic phases of La2CuO4 and the tetragonal phase of La2NiO4. The calculations are in fair agreement with reported experiments. The computed phonon dispersion in the tetragonal phase of La2CuO4 reproduces the soft mode behaviour for the lowest Σ4 TO branch which is found to harden in the orthorhombic phase, consistent with experimental data.
Volume 42 | Issue 6
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