Probing NaCl at High Pressure through Optical Studies and Ab Initio Calculations

Abstract

The optical constants of sodium chloride in a wide pressure range were determined from the analysis of the reflectance and transmittance spectra of a minute quantity of NaCl powder placed in diamond anvil cells. The so-called "reststrahlen band" dominates the far-infrared reflectance spectra shifting from 150 cm −1 to 500 cm −1 at 100 GPa. For the 0−17.5 GPa pressure range, measurements allow accurate determination of both transverse and longitudinal mode frequencies. Higher pressure measurements reveal the B1 → B2 structural transition around 30 GPa and provide frequencies for the transverse and longitudinal modes. This spectroscopic signature on a sample smaller than 100 μm using light of a wavelength close to this dimension was observed, thanks to the high brilliance synchrotron source. In addition, ab initio calculations performed for the 0−200 GPa range predict the TO and LO frequencies. They are validated by the excellent agreement with the experiment.

IR Spectroscopy of PbZr1–xTixO3 Material: A Complementary Experimental/Ab Initio Calculations Approach of a Solid Solution

“…Nevertheless, this interpretation which may allow a better agreement with the experimental spectra, implies the detection of LO modes through transmission. This could only be the case for important reflectance between TO and LO mode frequencies, causing a dip in the transmission measurements, in a similar fashion as observed in NaCl …”

“…This could only be the case for important reflectance between TO and LO mode frequencies, causing a dip in the transmission measurements, in a similar fashion as observed in NaCl. 43 Conclusions. The present study brings the first determination through modeling of the ferroelectric/dynamical properties of various compositions of PZT.…”

Infrared phonon spectroscopy on the Cairo pentagonal antiferromagnet Bi2Fe4O9: a study through the pressure induced structural transition

“…As described by Langerome et al 36 , the interface with a diamond affects the baseline in the low frequency side of the reflectivity band and should be considered in the fitting model of quasi-normal reflectivity. Using the Ref-Fit software 31 , we attempted to simulate the effect of the interface with the diamond, but found out only a negligible effect of the diamond interface with respect to interferences and diffraction effects dominating at low frequencies.…”

Synthesis of rare-earth metal compounds through enhanced reactivity of alkali halides at high pressures

“…Indeed, NaCl and KCl were thought to be chemically inert over wide pressure (up to 200 GPa) and temperature (up to 3000 K) ranges 1 . Therefore, they have often been used as pressure calibrants 2 , pressure transmitting media 3 , and electrical and thermal insulators in HP experiments 3 – 5 . Recent experimental and theoretical studies 6 – 8 suggest, however, that the behavior of the Na-Cl and K-Cl systems at HP is complex, and several compounds with an unusual stoichiometry (like NaCl 3 , Na 3 Cl, Na 2 Cl, and KCl 3 ) have been reported.…”