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Analysis of isothermal equations of state for ionic solids and geophysical minerals at high temperatures
Sharma Rekha, Bindu Sharma

The design, operation, and pressure calibration of an opposed movement multi-anvil device, OMMAD, are described. A finite-element analysis of the tungsten carbide anvils of this apparatus is made with the use of a Mohr – Coulomb derived criterion. The results are in excellent agreement with the experimental pressure calibration curve. Controlled support stress is applied on the flanks of the anvils to improve their mechanical capabilities, and the stress distributions in the anvils are presented. The OMMAD is able to produce pressures of 20 GPa using tungsten carbide anvils. It does not exhibit design-related limitations on the cell volume as a function of maximum pressure, in contrast to current high-pressure devices. Large-volume devices for pressures of 20 GPa can now be developed for high-temperature, high-pressure experiments. The pressure range for industrial production is therefore extended from 5 – 6 GPa to 20 GPa.

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