SMALL LATTICE MISMATCHES IN HIGHLY IMPERFECT SINGLE-CRYSTALS - A PROBE INTO PHASE SPECIFIC STRAINS AND STRESSES .1. DETERMINATION BY MEANS OF DIFFRACTION MAPPINGS

A formalism is proposed for the evaluation of small lattice mismatches in the order of 10(-3) occurring in technical single crystals with st rong defect structure by means of two-dimensional intensity profiles. Such diffraction mappings include the whole information referring to o rientation distributions and variations of interplanar spacings. Resul ts from high-resolution experiments can be reduced to a conventional o ne-dimensional intensity distribution by an integration with respect t o the orientation distribution. Common methods for analyzing diffracti on mappings are unsuitable if instruments with low resolution are bein g used. Thus, the presented formalism separates the instrumental peak broadening from material properties using a two-dimensional analytical deconvolution considering not vanishing beam divergence as well as a broad wavelength distribution. A conversion of any material model into an analytical function is possible. The resulting functions can be fi tted into diffraction mappings using a nonlinear least-squares procedu re. Both, the constrained lattice mismatch as well as the phase specif ic lattice parameters, can be determined.