After pressurization to 30 GPA, in a diamond anvil cell, benzene transforms, at room temperature, to a white solid which is stable at ambient pressure. We report here the infrared spectroscopy analysis performed under pressure and at ambient conditions. These preliminary results show that the transformation involves an opening of the benzene rings leading to a highly cross-linked polymer.

X-ray-absorption measurements of liquid and solid krypton at room temperature in the pressure range 0.1-30 GPa have been performed using the dispersive setup and diamond-anvil cells as a pressure device. The evolution of the near-edge structures as a function of pressure, including the first intense resonance, has been interpreted using multiple-scattering calculations. It is shown that the near-edge structures are reproduced taking into account two-body and three-body terms associated with the first-neighbor atoms. Extended x-ray-absorption fine-structure (EXAFS) spectra have been analyzed in the framework a multiple-scattering data-analysis approach taking proper account of the atomic background including the [1s4p], [1s3d], and [1s3p] double-electron excitation channels. Isobaric Monte Carlo (MC) computer simulations based on empirical pair potentials, as proposed by Barker (K2) and Aziz (HFD-B), have been performed to make a quantitative comparison of theoretical and experimental local structural details of condensed krypton at high pressures. From the analysis of EXAFS data we were able to obtain simultaneous information on average distance, width, and asymmetry of the first-neighbor distribution, as a function of pressure. These parameters yield a unique insight on the potential function because they are affected by both minimum position and curvature of the effective pair potential. The trend of the first-neighbor distribution as a function of pressure is in quantitative agreement with the HFD-B potential at moderate pressures, deviations are found at higher pressures where EXAFS spectra are very sensitive to the hard-core repulsive part of the potential. The weak EXAFS signal of liquid krypton at room temperature and 0.75 GPa has been found in accord with the results of the MC simulations within the noise of the measurement

CuInSz and CuInSez chalcopyrites have been studied up to 29 GPa in a diamond anvil cell by energy dispersive X-ray diffraction (EDX) using synchrotron radiation. Phase transitions have been observed at 9.5 and 7.6 GPa and the high-pressure phases have been indexed as cubic. The pressure dependence of the volume per formula unit has been fitted with a first-order Murnaghan equation of state. The bulk moduli are 75 and 72 GPa for the chalcopyrite phases and 123 and 114 GPa for the cubic phases of CuInS2 and CuInSe2, respectively. The volume reduction at the transition pressure is roughly 10%. The recovered phases are quite different from the initial ones. For CuInSe2 it is of the zincblende type, for CuInS2 it is an amorphous phase. Thus, the pressure-induced phase changes are not reversible.