# Treating different bonding situations: Revisiting Au-Cu alloys using the random phase approximation

## TL;DR

This paper demonstrates that the random phase approximation (RPA) effectively describes the ground state properties of copper-gold alloys, outperforming semi-local functionals in accuracy and capturing diverse bonding situations.

## Contribution

The study shows that RPA can accurately predict properties of Cu-Au alloys, highlighting its ability to handle different bonding scenarios better than traditional density functionals.

## Key findings

- RPA estimates lattice constants within 1.4% of experimental values.
- Semi-local functionals fail to accurately predict bulk moduli.
- RPA successfully describes the transition between different electron density states.

## Abstract

The ground state equilibrium properties of copper-gold alloys have been explored with the state of art random phase approximation (RPA). Our estimated lattice constants agree with the experiment within a mean absolute percentage error (MAPE) of 1.4 percent. Semi-local functionals such as the generalized gradient approximation (GGA) of Perdew, Burke, and Ernzerhof (PBE) and strongly constrained and appropriately normed (SCAN) fail to provide accurate bulk moduli, which indicate their inability to describe the system in a stretched or compressed state with respect to the equilibrium geometry. We find that the non-locality present in RPA is able to describe the transition between two delocalized electron densities (bulk elemental constituents to crystallized alloys), as required to provide accurate formation energies. Based on our results, we conclude that it is difficult to find a universal density functional which can give accurate results for a wide range of properties of intermetallic alloys. However, RPA can capture different bonding situations, often better than other density functionals. It gives accurate results for a wide range of ground state properties for the alloys, generated from metals with completely filled d-shells.