Force constant changes around defects in crystals

A direct method, based on a fairly standard use of the HADES package, for calculating the changes in force constants around defects is presented and illustrated with the example of an O2- interstitial in UO2. The force constant changes are those required in Green's function treatments of defect problems using core functions. As well as its simplicity, the method has the advantage that it includes the effects of changes in polarization which are usually omitted. Such effects are very important in the force constants for displacements which introduce electric fields at the defect site. (author)