Elasticity, shear strength, and equation of state of molybdenum and gold from x-ray diffraction under nonhydrostatic compression to 24 GPa
- Department of Geosciences, Princeton University, Princeton, New Jersey 08544 (United States)
- Consortium for Advanced Radiation Sources, The University of Chicago, 5640 South Ellis Avenue, Chicago, Illinois 60637 (United States)
- Geophysical Laboratory and Center for High-Pressure Research, Carnegie Institution of Washington, 5251 Broad Branch Road NW, Washington, DC 20015 (United States)
- Materials Science Division, National Aerospace Laboratories, Bangalore 5600 17, (India)
Lattice strains were measured as a function of the angle {psi} between the diffracting plane normal and the stress axis of a diamond anvil cell in a layered sample of molybdenum and gold. The sample was compressed over the range 5-24 GPa and the lattice strains were measured using energy-dispersive x-ray diffraction. As {psi} is varied from 0 degree sign to 90 degree sign , the mean lattice parameter of molybdenum increases by up to 1.2% and that of gold increases by up to 0.7%. A linear relationship between Q(hkl), which is related to the slope of the measured d spacing versus 1-3 cos{sup 2} {psi} relation, and 3{gamma}(hkl), a function of the Miller indices of the diffracting plane, is observed for both materials as predicted by theory. The pressure dependence of the uniaxial stress t for gold from this and other recent studies is given by t=0.06+0.015P, where P is the pressure in GPa. The uniaxial stress in molybdenum can be described by t=0.46+0.13P. Using gold as an internal pressure standard, the equation of state of molybdenum depends strongly on {psi}. The bulk modulus obtained from a Birch-Murnaghan fit varies from 210 to 348 GPa as {psi} varies from 0 degree sign to 90 degree sign . However, an equation of state in good agreement with shock and ultrasonic isotherms is obtained for {psi}=54.7 degree sign where the deviatoric contribution to the lattice strain vanishes. Second-order elastic moduli for gold and molybdenum are obtained from the data. The results are generally consistent with an earlier x-ray study and with extrapolations of low-pressure ultrasonic data. The pressure dependence of the shear modulus C{sub 44} is smaller for the x-ray data than predicted by extrapolation of ultrasonic data. (c) 1999 American Institute of Physics.
- OSTI ID:
- 20217871
- Journal Information:
- Journal of Applied Physics, Vol. 86, Issue 12; Other Information: PBD: 15 Dec 1999; ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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