Absence of High-Pressure Ground-State Reentrant Ferroelectricity in PbTiO_{3}.

We study ferroelectricity in the classic perovskite ferroelectric PbTiO_{3} to high pressures with density functional theory (DFT) and experimental diamond-anvil techniques. We use second harmonic generation spectroscopy to detect lack of inversion symmetry. Consistent with early understanding and experiments, we find that ferroelectricity disappears at moderate pressures.

Pressure dependence of intermediate-range order and elastic properties of glassy Baltic amber.

Amber is a unique example of a fragile glass that has been extensively aged below its glass transition temperature, thus reaching a state that is not accessible under normal experimental conditions. We studied the medium-range order of Baltic amber by x-ray diffraction (XRD) at high pressures. The pressure dependences of the low-angle XRD intensity between 0 and 5 Å^{-1} were measured from 0 to 7.

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).

Acoustic properties, elasticity, and equation of state of glycerol under pressure.

We employed high-pressure Brillouin scattering to study the pressure dependencies of acoustic modes of glycerol up to 14 GPa at 300 K. We observed longitudinal acoustic velocities and transverse acoustic velocities for the first time from 5 to 14 GPa. The results allow the determination of a complete set of elastic properties and an accurate determination of the pressure-volume (P-V) equation of state (EOS).

Sound Velocity and Equation of State of Ballistic Gelatin by Brillouin Scattering.

Brillouin scattering spectroscopy with diamond anvil cells was used by measuring the pressure dependence of the sound-relevant polymer material, glass-forming liquid, and HO (water and ice VII) velocities of the material from ambient pressure to 12 GPa at room temperature. Measurements of 20%, 10%, and 4% gelatin solutions were performed. For comparison purposes, we also measured the pressure dependence of the sound velocity of animal tissue up to 10 GPa.