Phonon spectrum of ZnAl2O4 spinel from inelastic neutron scattering and first-principles calculations

The phonon spectrum of ZnAl2O4 spinel was studied jointly by inelastic neutron-scattering and 1st-principles calcns. The results permit an assessment of important mech. and thermodynamical properties such as the bulk modulus, elastic consts., lattice sp. heat, vibration energy, and Debye temp. The obsd. generalized phonon d. of states shows a gapless spectrum extending to a cutoff energy of .apprx.840 cm-1. The theor. results reproduce all of the features of the phonon d. of states. The calcd. Raman-and IR-active phonon frequencies agree well with the data in the literature. A comparison of the lattice dynamics of ZnAl2O4 and MgAl2O4 spinels was carried out using a simple rigid-ion model, which shows that the major difference in the phonon frequencies of the 2 materials can be accounted for by the mass effects between the Zn and Mg ions. [on SciFinder (R)]