Ab-Initio Calculation of the Lattice Relaxation in Dilute Alloys

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Electronic structure calculations for point defects in metals usually neglect the lattice distortion in the neighborhood of the defect. In fact, a reliable theoretical prediction of the perturbed lattice geometry around impurities is a rather complicated task because it requires accurate total-energy and/or force calculations. From the experimental point of view detailed information about the local geometry in the vicinity of a defect can be obtained by extended X-ray-absorption-fine-structure (EXAFS) measurements.1 Inclusion of lattice distortion is important for a more realistic description of the electronic structure of point defects in bulk systems, while it becomes crucial in the case of defects on surfaces where the reduced coordination number induces a greater structural flexibility. Moreover, the study of the strain fields caused by the size mismatch between impurity and host atoms is interesting because they influence the interaction of solute atoms with other defects and the tendency towards long-range ordering or clustering