High Temperature High Pressure Study Of The R₁ Ruby Fluorescence Line

The ruby pressure scale, in which pressure is measured on the basis of R1 ruby fluorescence line, is one of the most widely used pressure scale in high pressure study. However, the ruby pressure scale is sensitive to temperature. At atmospheric pressure and 1100K ,the redshift is about 195cm-1,which is equal to the redshift when pressure is 26.7GPa at room temperature.This work mainly studies on the effect of HPHT to the R1 line, including HPHT experiments and some related theory calculations. The HPHT experiments (5GPa < P < 10GPa, 1300K < T < 2500K) are taken on the in situ Laser Heated Diamond Anvil Cell Raman (LHDAC-R) system, and the calculations are taken on Materials Studio running on high performance workstation.The in situ LHDAC-R system is based on double-sided laser heating technique and was constructed in our lab for the first time in the world. Heating the sample in a DAC by introducing laser energy into the DAC,we can perform in intu Raman scattering measurement at megabar pressures and temperatures higher than 3000K. With in situ LHDAC-R system,we have performed in situ HPHT Raman spectroscopy, new materials synthesis, searching for new HPHT state, etc. The error of temperature measurement bv spectral radiometry used on the m situ LHDAC-R system is less than 5%. However, the pressure is not measured in the DAC when laser heating sample as many people did before.In the HPHT experiments of this study, NaCl is chosen as pressure media and insulating material . To avoid the pressure grads ,the size of ruby chip is about 10 m. Gasket is made of T301 stainless steel with a 100 m hole. Four experiments were performed in which the pressures before heating are 5.5,6.9,8.0,9.6GPa . In the former two impressed gaskets are used and inthe latter two not. The power of laser is adjusted while heating for elevating temperature,and the burning state of sample in DAC is watched using monitor. When the sample burns tranquilly,the ruby fluorescence and thermal radiation spectrum are measured.The experiment results tell us that redshift of RI line under HPHT condition is smaller than the one under the same temperature and atmospheric pressure.lt shows that high pressure decreases the redshift of temperature.The redshift of HPHT is not equal to the sum of shift from pressure and temperature respectively.We used [CrO6]9~ as DFT calculation model in order to calculated effect of lattice aberration.lt shows that the redshift of Rj line occurs when the length of Cr-0 bond gets shorter; and blueshift of the R\ line occurs when the bond angle of O-Cr-0 becomes smaller.These results shows that RI line shift at HPHT is the effect of lattice aberration and electron phonon interaction(EPI). The former includes bond stretching of Cr-O and bond angle torsion of 0-Cr-O,while the latter includes acoustic branches and optical branches.More DFT calculations of energy band structures on ALjyCrOyj have been accomplished. The calculation results have a large error ,because the model is too small.The ab initio calculations in this paper are better than old calculations , such as crystal field theory(CFT).The anisotropy which is neglected in CFT calculations is considered in ab initio ones . Moreover, CFT calculations need the empirical parameters fitted from experiments but ab initio calculations not .The calculations in this paper are more reasonable than before .To obtain the HPHT energy band structures of ruby by ab initio calculations, Al2o3CrO3o6 is a more reasonable model. This model is very large and computationally expensive .Some calculations will soon be performed.