# Theoretical evidence for unexpected O-rich phases at corners of MgO surfaces

## TL;DR

This study uses advanced computational methods to reveal that corner defects on MgO surfaces can host unexpected oxygen-rich phases, influenced by atomic coordination and environmental conditions.

## Contribution

It provides the first theoretical evidence that corner sites on MgO surfaces can stabilize O-rich phases under certain conditions, challenging previous assumptions.

## Key findings

- Corner defects can host unexpected O-rich phases.
- Manipulating atomic coordination alters surface stability.
- Surface chemistry depends on environmental oxygen levels.

## Abstract

Realistic oxide materials are often semiconductors, in particular at elevated temperatures, and their surfaces contain undercoordiated atoms at structural defects such as steps and corners. Using hybrid density-functional theory and ab initio atomistic thermodynamics, we investigate the interplay of bond-making, bond-breaking, and charge-carrier trapping at the corner defects at the (100) surface of a p-doped MgO in thermodynamic equilibrium with an O2 atmosphere. We show that by manipulating the coordination of surface atoms one can drastically change and even reverse the order of stability of reduced versus oxidized surface sites.