Plastic deformation of either a sample or a gasket between diamond anvils leads to large pressure concentrations, i.e., the maximum pressure can be many times the average pressure. This behavior is discussed using elementary plasticity theory for the case where the pressures are sufficiently low that the yield stress can be assumed not to vary with pressure. It is then shown that the pressure concentration factor can be even much larger when the yield stress of the sample (or gasket) at the highest pressure is much greater than the yield stress at the lowest pressure. This is illustrated with solid xenon where it is shown that the assumption that Nelson and Ruoff Phys. Rev. Lett.42, 383 (1979) made about the pressure distribution in their xenon samples is incorrect. The pressure distribution is shown to be much steeper than they assumed. Thus, the pressure they had when they observed electrical conduction in xenon was, so far as the evidence of the present analysis shows, above 1 Mbar.
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