Dynamical and dielectric properties of MP2O7 (M = Ti, Zr, and Hf): A first-principles investigation

A first-principles investigation on the structural and vibrational properties of MP2O7 (M = Ti, Zr and Hf) has been performed. Using density functional perturbation theory, the Born effective charge tensors, the IR-active phonon frequencies at the center of the Brillouin zone, and the dielectric constants of MP2O7 are obtained. Due to the complex structure of MP2O7, the Born effective charge tensors are quite complex. The anomalously large values of Z* implies the covalent bonding nature of MP2O7. The frequencies of zone center IR-active modes are closely related to the local structural and chemical environments of atoms. The electronic and static dielectric permittivities are analyzed in detail. The theoretical results highlight the vital role of MO6 octahedron underpinning the properties of MP2O7.