Layer and bulk phonon modes in the YBa 2Cu 3O 6 compound

Abstract

The layer description of the phonon subsystem of the YBa 2Cu 3O 6 lattice has been performed. A group-theory analysis and model dynamical calculations were carried out both for isolated layers and for the bulk YBa 2Cu 3O 6 structure. The correspondence between layer and bulk modes has been established. It has been shown that acoustic modes of isolated layers give rise to acoustic bulk modes Γ ac and interlayer bulk modes Γ inter, and optical vibrations of isolated layers induce intralayer bulk modes Γ intra. The set of vibrations in the Brillouin zone center is given by the expression Γ = 3 Γ ac + 15 Γ inter + 18 Γ intra.