A study was made of local strain effects associated with vacancy defects in

strontium titanate and the first calculations of elastic dipole tensors and chemical

strains for point defects in perovskites were reported. The combination of local and

long-range results was expected to permit the determination of X-ray scattering

signatures that could be compared with experiment. It was found that the oxygen

vacancy possessed a special property. This was a highly anisotropic elastic dipole

tensor which almost vanished upon averaging over all possible defect orientations.

By direct comparison with experimental measurements of chemical strain,

constraints were placed upon the possible defects present in oxygen-poor strontium

titanate and a conjecture was introduced regarding the nature of the predominant

defect in strontium-poor stoichiometries in samples grown via pulsed laser

deposition. Recent experimental data, on strontium titanate films deposited via

molecular-beam epitaxy, well-supported the present calculated value of the

chemical strain associated with strontium vacancies.

Elastic Effects of Vacancies in Strontium Titanate: Short- and Long-Range Strain

Fields, Elastic Dipole Tensors, and Chemical Strain. D.A.Freedman, D.Roundy,

T.A.Arias: Physical Review B, 2009, 80[6], 064108