Tackling Disorder in γ-Ga₂O₃

Ga₂O₃ and its polymorphs are attracting increasing attention. The rich structural space of polymorphic oxide systems such as Ga₂O₃ offers promising potential for electronic structure engineering, which is of particular interest for a range of energy applications, such as power electronics. γ-Ga₂O₃ presents a particular challenge across synthesis, characterisation, and theory due to its inherent disorder and resulting complex structure -- electronic structure relationship. Here, density functional theory is used in combination with a machine learning approach to screen a large number of potential structures, and thereby develop a robust atomistic model of the γ-phase. Theoretical results are compared with surface and bulk sensitive soft and hard X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and photoluminescence excitation spectroscopy experiments representative of the occupied and unoccupied states of γ-Ga₂O₃. This work presents a leap forward in the treatment of complex, disordered oxides and is a crucial step towards exploring how their electronic structure can be understood in terms of local coordination and overall structure.