Correction of diffraction optics and P-V-T determination using thermoelastic equations of state of multiple phases

This report discusses a new method to determine experimental pressure-volume-temperature (P-V-T) data and to correct misalignment of diffraction optics using thermoelastic equations of state of multiple phases. Analytical approaches as well as numerical approaches are presented for the technique. A number of phase combinations yield the best experimental result and the whole-pattern Rietveld and/or Le Bail refinement of diffraction patterns of multiple phases is a significant aspect of the technique. Specific examples indicate that the corrected pressure, temperature and diffraction optics are robust. Errors are estimated from the uncertainties of the measured cell dimensions. The error propagation for different experimental cases is discussed, along with the conditions and limitations of the method. This technique for P-V-T determination and the correction of diffraction optics is crucial for experiments conducted under extreme conditions of high pressure, high temperature and dynamic reactions.