Point defects

Abstract

Examples of intrinsic and extrinsic point defects are discussed. Models of point defects in a continuum as misfitting spheres are solved for rigid and deformablemisfitting spheres. Free surfaces alter significantly the formation volume of a point defect even when the point defect is far from any free surface. Many point defects have non-sperical symmetry, and it is then better to consider defect forces exerted by the point defect on neighbouring atoms. Defect forces capture the symmetry of the point defect in its local environment. Interaction energies between point defects and between point defects and other sources of stress are expressed conveniently and with physical transparency in terms of dipole, quadrupole etc. tensors of point defects and derivatives of the Green’s function. The dipole tensor is experimentally measurable through the lambda-tensor, which measures the derivative of the macroscopic strain of a crystal with concentration of the point defect.