Electronic band structure and inter-atomic bonding in layered 1111-like Th-based pnictide oxides ThCuPO, ThCuAsO, ThAgPO, and ThAgAsO from first principles calculations

TL;DR

This study uses first-principles calculations to analyze the electronic structure and bonding in Th-based layered pnictide oxides, revealing their semimetallic nature and mixed ionic-covalent bonding characteristics.

Contribution

It provides the first detailed electronic and bonding analysis of ThCuPO, ThCuAsO, ThAgPO, and ThAgAsO, highlighting their semimetallic properties and complex bonding.

Findings

Th-based pnictide oxides are semimetals.

Th 5f states are active and itinerant.

Bonding is a mixture of ionic and covalent contributions.

Abstract

First-principles FLAPW-GGA band structure calculations were employed to examine the structural, electronic properties and the chemical bonding picture for four ZrCuSiAs-like Th-based quaternary pnictide oxides ThCuPO, ThCuAsO, ThAgPO, and ThAgAsO. These compounds were found to be semimetals and may be viewed as "intermediate" systems between two main isostructural groups of superconducting and semiconducting 1111 phases. The Th 5f states participate actively in the formation of valence bands and the Th 5f states for ThMPnO phases are itinerant and partially occupied. We found also that the bonding picture in ThMPnO phases can be classified as a high-anisotropic mixture of ionic and covalent contributions: inside [Th2O2] and [M2Pn2] blocks, mixed covalent-ionic bonds take place, whereas between the adjacent [Th2O2]/[M2Pn2] blocks, ionic bonds emerge owing to [Th2O2] \to [M2Pn2] charge transfer.