Pb$_9$Cu(PO$_4$)$_6$O is a charge-transfer semiconductor

TL;DR

This study uses density functional theory to analyze the electronic structure of Pb$_9$Cu(PO$_4$)$_6$O (LK-99), revealing it as a charge-transfer semiconductor incompatible with superconductivity.

Contribution

It provides the first detailed theoretical analysis of LK-99's bandstructure, clarifying its semiconducting nature and challenging claims of superconductivity.

Findings

LK-99 is a charge-transfer semiconductor

The material's electronic structure does not support superconductivity

Further studies needed on doping and magnetic interactions

Abstract

By means of density functional theory and constrained random phase approximation we analyze the bandstructure of Pb$_9$Cu(PO$_4$)$_6$O (named LK-99). Our data show that the lead-phosphate apatite LK-99 in the proposed Cu-doped structure is a semiconductor with predominant charge-transfer nature, a result incompatible with a superconducting behaviour. In order to understand the interesting electronic and magnetic properties of this compound, it will be necessary to study the actual response to doping, the possibility of alternative structural and stoichiometric (dis)orders and to clarify the magnetic interactions as well as their impact on the electronic structure.