- 期刊
- OpenAccess
Zone-Centre Phonon Frequencies of Oxide Spinels
並列摘要
Lattice dynamical calculations have been performed for oxide spinels using the proposed theoretical model. In this model, the dynamical matrix is split into two parts: (i) the short-range part, and (ii) the long-range part. The short-range part is evaluated by using a Taylor expansion of the potential energy in the harmonic approximation, and the long-range part is evaluated on the basis of the screened-Coulomb potential. This model is applied to study the zone-centre (Γ=0) phonon frequencies of oxide spinels MCr2O4 (M=Mn, Zn). The significant outcome of the present work is that (i) the tetrahedral M-S force constants are smaller than the respective octahedral (Cr-S) ones, (ii) the bending-force constants are negligible, and (iii) the effective dynamical charges of the bivalent metal ions are nearly zero. The zone-center phonon frequencies calculated in this manner are found to be in very good agreement with the observed results.