First-principles study of low $\Sigma$ grain boundaries in CdTe

Grain boundaries (GBs) play critical roles in determining physical properties of polycrystalline materials. In this study, we investigate stability and electronic structure of GBs in CdTe through first-principles density functional calculations. We consider low $\Sigma$ symmetric tilt GBs including $\Sigma$3 (111), $\Sigma$3 (112), $\Sigma$5 (120), and $\Sigma$5 (130) GBs. We find that the $\Sigma$3 (111) GB is more stable than the other GBs considered in this study because it contains no dangling bonds and wrong bonds. The stability of the $\Sigma$3 GBs is independent on the chemical potential of Cd and Te whereas that of the $\Sigma$5 GBs depends on the chemical potentials. Unexpectedly, we find that the $\Sigma$5 (120) GBs are able to be more stable than the $\Sigma$3 (112) GBs, despite that the $\Sigma$3 (112) GBs have often been used as a model system to study GBs in polycrystalline thin-film photovoltaic materials. The $\Sigma$5 (120) GBs found in this study are not electrically harmful even though the GBs contain wrong bonds.