Ruby fluorescence pressure scale: Revisited

Effect of non-hydrostatic stress on X-ray diffraction in diamond anvil cell (DAC) is studied. Pressure gradient in sample chamber leads to the broadening of the diffraction peaks, which increase with the hkl index of the crystal. It is found that the difference between the determined d-spacing compressive ratio d/d₀ and the real d-spacing compressive ratio d_r/d₀ is determined by the yield stress of the pressure transmitting media (if used) and the shear modulus of the sample. On the basis of the corrected experiment data of Mao et al. (MXB86), which was used to calibrate the most widely used ruby fluorescence ruby scale, a new relationship of ruby fluorescence pressure scale is corrected, i.e., P=(1904/9.827)(1+Δλ/λ₀)^9.827-1.