HR: 16:00h
AN: DI44A-01 INVITED    [Abstracts]
TI: Static and Dynamic Equations of State: Key Challenges and Solutions
AU: * Duffy, T S
EM: duffy@princeton.edu
AF: Department of Geosciences, Princeton University, Princeton, NJ 08648, United States
AB: Together with the crystal structure, the equation of state is the most fundamental parameter obtained from high- pressure investigations. Each year a large number of papers are published whose main objective is accurate determination of the equation of state of various materials. However, challenges in equation of state measurement abound, and it is fair to say that many of these papers fail to achieve their goal, or at least fail to demonstrate that they have achieved their goal. In this paper, I will review the current status of equation of state measurement on geomaterials, focusing especially on the challenges associated with measurements to Mbar pressures. A significant dilemma in equation of state measurements is the trade-off between measurement accuracy and pressure range. The crux of the problem is the need to maximize pressure range while minimizing the contribution from deviatoric stress. Recent developments in radial x-ray diffraction have greatly advanced our understanding of differential stresses, and their application to equations of state will be discussed. The usefulness of direct elasticity measurements such as Brillouin scattering for accurate equations of state will be demonstrated with several recent examples. Shock compression methods are evolving rapidly and continue to play an important role in equation of state measurement. New dynamic quasi-isentropic compression measurements to multi-megabar pressures are promising but further highlight the importance of characterizing shear stresses at ultrahigh pressures. New Hugoniot data for metals such as gold can be used to sort out uncertainties in pressure scales at Mbar conditions. Finally, it has been noted that some materials such calcium fluoride and oxide garnets adopt virtually incompressible high-pressure phases above 1 Mbar under shock loading (Nellis and Petach, 2007). New static high-pressure measurements can shed light on the equation of state and structure of these materials under such conditions.
DE: 3919 Equations of state
DE: 3924 High-pressure behavior
DE: 3944 Shock wave experiments
SC: Study of the Earth's Deep Interior [DI]
MN: 2007 Fall Meeting