Characterization and atomic modeling of an asymmetric grain boundary

Grain boundaries (GBs) significantly affect the properties of materials. In an effort to examine the phenomena at GBs, many model boundaries, typically symmetric tilt GBs, have been investigated. However, the geometries of symmetric tilt GBs are too restricted to represent commonly occurring interface phenomena properly in polycrystalline materials. Thus, a method of applying density functional theory (DFT) to asymmetric GBs has long been desired. Here, we present a simple geometric method and a new GB model with two surfaces which make it possible to characterize an asymmetric tilt GB and calculate the GB energetics. Our method can be extended to study other geometric asymmetric interfaces in various materials. The proposed technique thus paves the way for DFT-related studies of asymmetric interfaces.