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Instability of the CsCl Structure in Ionic Solids at High Pressures

1985; American Physical Society; Volume: 54; Issue: 6 Linguagem: Inglês

10.1103/physrevlett.54.570

1092-0145

Yogesh K. Vohra, Steven J. Duclos, Arthur L. Ruoff,

Chemical Thermodynamics and Molecular Structure

It is shown by a simple model calculation that the ionic solids in the CsCl phase transform discontinuously to a tetragonal phase under high pressures at a fractional volume in the neighborhood of 0.5. This general result follows as a consequence of competing Madelung energy and repulsive energy terms. The $\frac{c}{a}$ variation with pressure and transition volume fraction are in approximate agreement with the recent ultrahigh pressure experiments on cesium halides.