SINGLE CRYSTAL STUDIES IN THE Mbar RANGE. P.Loubeyre and R.LeToullec, PMC, Universite Paris 6, Paris, France
Single-crystal x-ray diffraction at Mbar pressure has been a major goal of high pressure physics. It is the essential technique to obtain diffracion from low -Z elements and can provide the most accurate structural data possible. But taking any single-crystals to very high pressures is extremely difficult as they usuallly break beyond use. Also, the diamond anvil cell should have an x-ray viewing angle of both sides of the sample as large as 80deg., that is a mechanical challenge.
We will present a new x-ray cell with boron seats of half-sphere geometry that can hold the massive support on the diamond for the Mbar presures. The use of a soft hydrostatic cushion (helium at best and gold when it is impossible to load) will be shown to prevent the break up of the crystal. Already, single crystals of H2, He, LiH, H2O, Ar(H2)2, Ne(He)2 have been studied in the Mbar range.
H2 and H2O will be selected as the most illustrative examples. Hydrogen because it is considered as the utmost difficult system for x-ray study at high pressure. H2O because our single-cystal measurements can be compared to various powder x-ray diffraction works.