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New model for the shock‐induced &agr;‐quartz→stishovite phase transition in silica

 

作者: J. C. Boettger,  

 

期刊: Journal of Applied Physics  (AIP Available online 1992)
卷期: Volume 72, issue 11  

页码: 5500-5508

 

ISSN:0021-8979

 

年代: 1992

 

DOI:10.1063/1.351945

 

出版商: AIP

 

数据来源: AIP

 

摘要:

A new model has been developed to describe the &agr;‐quartz to stishovite phase transition in silica under shock‐loading conditions. During hydrodynamic simulations, individual global equations of state for the &agr;‐quartz and stishovite phases of silica are mixed in accordance with process‐dependent constraints on the Gibbs free energy difference between the phases (&Dgr;G). For the shock‐induced transition, &Dgr;Gis required to equal a simple two parameter function of the mass fraction of stishovite. Unlike previous models, the new constraint equation assumes that the shock induced phase transition begins at the equilibrium phase boundary, but is not completed unless peak stresses on the order of 40 GPa are achieved. On release, the reverse transition is required to satisfy the usual thermodynamic equilibrium condition (&Dgr;G=0). It is shown that hydrodynamic simulations combining this hysteretic phase transition model with a strength model that assumes partial softening after yielding are capable of reproducing experimental Hugoniot and release data for crystalline silica in the mixed‐phase region.

 

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