Theoretical analysis of R-line shifts of ruby subjected to different deformation conditions

A theoretical approach to analyzing ruby R-line wavelength shifts under different types of deformation (uniaxial-strain compression and tension under shock loading, hydrostatic compression, and uniaxial-stress compression) and for different crystallographic orientations is presented. A symmetry-adapted representation of the various loading conditions in conjunction with crystal-field theory, but no point-ion model, is used to relate the shift of the R lines to deformation. The parameters needed in the model are obtained from shock-wave-compression data along the c and a axes. Without further iteration, these parameters are used in a consistent manner to analyze all remaining data: shock-wave-tension results, hydrostatic results, and uniaxial-stress results for different crystal orientations. Very good agreement is obtained between theoretical predictions and measurements. Changes in local site symmetry have been related to macroscopic deformation. For nonhydrostatic loading, effects of crystal orientation are important in analyzing R-line wavelength shifts. Suggestions for using ruby calibration at high pressures in diamond-anvil-cell measurements are presented. Implications of the present work for understanding shock-wave deformation in crystalline solids are indicated