Density functional theory analysis of the effect of structural configurations on the stability of GaAsBi compounds

[Display omitted] •Higher Bi concentrations promote Bi clustering in GaAsBi compounds.•Linear and planar arrangements favored over there-dimensional clusters.•Small Bi concentrations and ensemble sizes favor linear arrangement in [1 0 0] direction.•Larger Bi concentrations and ensembles favor [1 0 1] lines and (1 1 1) planes. The aggregation of Bi atoms exhibits significant influence on the stability and electronic properties of GaAsBi compounds. Here, density functional theory calculations are used to probe stabilities of different configurations of Bi atoms substituted for As at concentrations below 4% of available As sites. The configurations examined include ensembles of four or eight Bi atoms with large Bi-Bi distances (dispersed configuration) or Bi atoms occupying contiguous As sites (aggregated configurations) in periodic supercells of different sizes. The stabilities of GaAsBi compounds decrease with increasing Bi concentration. This decrease in stability is more significant for dispersed than aggregated configurations, which leads to increased favorability for the aggregation of Bi atoms at higher concentration. Among the aggregated arrangements, the linear and planar ones are much more stable than the three-dimensional arrangements at all concentrations. The stabilities also depend significantly on ensemble sizes of Bi atoms, with enhanced stability for linear [1 0 1] and planar (1 1 1) configurations in eight atom ensembles than in four atom ensembles of similar concentration. These results demonstrate distinct effects of concentration and ensemble size on the preferred configuration and suggest that accurate large-scale simulations of doped GaAs compounds require models that incorporate not only atom-pair interactions but also long-range interactions among aggregates.