Polarization and dynamical charge of ZnO within different one-particle schemes

Abstract

We calculate ab initio the electronic states, spontaneous polarization P, and Born dynamical charge ${\mathit{Z}}^{\mathrm{*}}$ of ZnO, using the local-density approximation (LDA), the Hartree-Fock (HF), and a model GW scheme. Upon going from HF to GW and to LDA, the d bands raise substantially in energy, the model GW providing the best overall agreement with experiment. By contrast, the three schemes give the concordant values P=-0.047 C/${\mathrm{m}}^2$ and ${\mathit{Z}}^{\mathrm{*}}$=±2.1, in agreement with available experimental data. While the value of ${\mathit{Z}}^{\mathrm{*}}$ suggests a rigid-ion-like behavior of ZnO, its band-by-band decomposition reveals anomalous contributions from O 2s, Zn 3d, and O 2p bands, indicating a substantial interaction between the corresponding occupied atomic orbitals.