equation of state of boron carbide.

We report the equation of state measurements of BC to 50 GPa and approximately 2500 K in laser-heated diamond anvil cells. We obtain an ambient temperature, third-order Birch-Murnaghan fit to the data that yields a bulk modulus of 221(2) GPa and derivative, (d/d) of 3.3(1).

Optical cell for in situ vibrational spectroscopic measurements at high pressures and shear.

An optical cell is described for performing simultaneous static high-pressure and shear experiments. This cell design is a modification of the previously designed megabar diamond anvil cell used by Mao and Bell that allows for controlled, remote shear. With this diamond anvil cell, it is possible to use a wide range of existing experimental techniques and pressure media.

High-pressure vibrational spectroscopy of energetic materials: hexahydro-1,3,5-trinitro-1,3,5-triazine.

Vibrational spectroscopy has been used to investigate the room-temperature high-pressure phases of the energetic material hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). The pressure-induced alterations in the spectral profiles were studied in a compression sequence to 30.2 GPa using Raman spectroscopy and to 26.

Inelastic neutron scattering spectrum of cyclotrimethylenetrinitramine: a comparison with solid-state electronic structure calculations.

Solid-state geometry optimizations and corresponding normal-mode analysis of the widely used energetic material cyclotrimethylenetrinitramine (RDX) were performed using density functional theory with both the generalized gradient approximation (BLYP and BP functionals) and the local density approximation (PWC and VWN functionals). The structural results were found to be in good agreement with experimental neutron diffraction data and previously reported calculations based on the isolated-molecule approximation. The vibrational inelastic neutron scattering (INS) spectrum of polycrystalline RDX was measured and compared with simulated INS constructed from the solid-state calculations.

Structural and vibrational characterization of tetracyanoethylene-hexamethylbenzene as a function of pressure.

The neutron powder diffraction and inelastic neutron scattering (INS) spectra of the electron donor-acceptor complex, tetracyanoethylene-hexamethylbenzene have been studied as a function of pressure to 0.414 GPa. Using the PW91 and PBE density functional theories, the unit cell vectors were calculated as a function of pressure and are compared to those experimentally obtained from the diffraction data.