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Lattice- And Molecular-Dynamics Studies Of Rbliso4, V. Katkanant, John R. Hardy

John R. Hardy Papers

Using our previously developed method for calculating parameter-free potential-energy surfaces for ionic molecular crystals, specifically sulfates, we study phase transitions in RbLiSO₄ by means of lattice and molecular dynamics. We found that the high-temperature phase I (Pnam) is highly unstable and transforms to the observed lower temperature phase VI (P1121/n) at about 475–525 K. Compared with isomorphous CsLiSO₄, there are more branches of unstable modes in the Pnam phase for RbLiSO₄. The maximum instability of these modes occurs away from the zone center, q=(0.118a*,0,0), which implies that a high-order …