First-principles studies of ground- and excited-state properties of MgO, ZnO, and CdO polymorphs

TL;DR

This study uses first-principles calculations to analyze the structural, electronic, and optical properties of various polymorphs of MgO, ZnO, and CdO, revealing insights into their stability and electronic behavior.

Contribution

It provides a comprehensive ab initio analysis of multiple polymorphs of MgO, ZnO, and CdO, including stability under pressure and strain, and examines the role of d electrons in their properties.

Findings

Stability of ground-state phases under pressure and strain.

Band structures and dielectric functions of all polymorphs.

Physical explanation for trends in geometry and band gaps.

Abstract

An ab initio pseudopotential method based on density functional theory, generalized gradient corrections to exchange and correlation, and projector-augmented waves is used to investigate structural, energetical, electronic and optical properties of MgO, ZnO, and CdO in rocksalt, cesium chloride, zinc blende, and wurtzite structure. In the case of MgO we also examine the nickel arsenide structure and a graphitic phase. The stability of the ground-state phases rocksalt (MgO, CdO) and wurtzite (ZnO) against hydrostatic pressure and biaxial strain is studied. We also present the band structures of all polymorphs as well as the accompanying dielectric functions. We discuss the physical reasons for the anomalous chemical trend of the ground-state geometry and the fundamental gap with the size of the group-II cation in the oxide. The role of the shallow Zn3d and Cd4d electrons is critically examined.