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### Finite-element modeling and ab initio calculations of megabar stresses in the diamond anvil cell

**S. Merkel**, R.J. Hemley, H.K. Mao and D.M. Teter

Finite-element modeling calculations are conducted to investigate the remarkably large elastic strains in diamond observed in ultrahigh pressure diamond anvil cell experiment. We perform ab initio calculations to evaluate the elastic properties of diamond in the multimegabar range and use the finite-element results to estimate the pressure dependence of shear stress of strong materials used as gasket. We then analyze the influence of geometric properties such central flat diameter or bevel angle, and reveal the existence of two distinct deformation mechanisms during the pressure increase. Finally, we investigate the stress conditions in the gasket and the diamond and discuss possible shear-induced mechanical instabilities in diamond.