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Diamond and gold powders were compressed nonhydrostatically in a diamond anvil cell and examined by x-ray diffraction using a radial geometry to evaluate the evolution of stresses and strains in these materials to ultrahigh pressure. We found that near isostrain continuity developed across diamond and gold grains under uniaxial compression. The observed mean pressure of diamond powder reached to 360(40) GPa while it was only 31(1) GPa for the polycrystalline gold under the highest load. Polycrystalline diamond can support a microscopic deviatoric stress of 160(18) GPa at about 360 GPa. Due to the deformation of the diamond anvil culet, the macroscopic differential stress of the diamond sample was limited to about 43(8) GPa. There is no evidence that the diamond grains have yielded in our experimental pressure range. [ABSTRACT FROM AUTHOR]

Pure-phase polycrystalline cadmium tetraphosphide (CdP4) has been successfully synthesized under high pressures in a large volume cubic press, and the pressure-temperature (P-T) formation boundary of CdP4 from the Cd-P binary system has been determined. The equation of state of monoclinic CdP4 has also been evaluated by synchrotron-radiation angle-dispersive X-ray diffraction (ADXRD) under quasihydrostatic compression up to 26.4 GPa in a diamond-anvil cell. The ADXRD data yield a bulk modulus B0 = 94 ± 9 GPa with a pressure derivative B0′ = 8.0. The experimental data are discussed and compared to the results of first-principles calculations. [ABSTRACT FROM AUTHOR]

The compression behavior and stress state of nanocrystalline tungsten boride (WB) were investigated using radial x-ray diffraction (RXRD) in a diamond-anvil cell under non-hydrostatic compression up to 60.4 GPa. The compression properties and stress state are analyzed using lattice strain theory. Experiments were conducted at beamline X17C of the National Synchrotron Light Source. The radial x-ray diffraction data yield a bulk modulus that is qualitatively consistent with density functional theory calculations and demonstrate that WB is a highly incompressible material. A maximum differential stress, t, of about 14 GPa can be supported by nanocrystalline WB at the highest pressure. This corresponds to about 5% of the shear modulus, G, which is smaller than the values of t/G (∼8%-10%) observed for BC2N, B6O, TiB2, and γ-Si3N4 at high pressures. Thus, while WB is highly incompressible, its strength is relatively low at high pressures compared to other hard ceramics. [ABSTRACT FROM AUTHOR]