antisite

An antisite defect is a point defect in a crystalline material in which an atom occupies a lattice site normally held by a different species. This type of defect is common in ordered compounds and multicomponent alloys that possess distinct sublattices, such as AB-type compounds, Heusler alloys, and double perovskites, where atoms from one sublattice occupy sites on another.

Antisite defects arise during crystal growth, cooling, irradiation, or diffusion processes that exchange neighboring atoms. The equilibrium concentration of antisites depends on the defect formation energy and temperature, typically following an Arrhenius relation. Annealing or heat treatment can reduce antisite disorder by promoting chemical ordering.

The presence of antisite defects can significantly affect material properties. They can alter electronic structure, carrier concentrations, and optical or magnetic behavior by introducing local distortions and scattering centers. Depending on the system, antisites may act as donors or acceptors, influence diffusion pathways, and disrupt long-range order, potentially driving order–disorder transitions or modifying phase stability.

Detection and study of antisites rely on techniques such as diffraction, which reveals diffuse scattering associated with disorder, as well as spectroscopy and stoichiometric analysis. Notable examples occur in Heusler alloys (where X, Y, and Z elements can exchange sites) and in double perovskites, where B-site cations swap positions. In semiconductors and other compounds, antisite defects are considered among intrinsic point defects that influence doping behavior and material performance.