lambda-transition of NH4Cl and ND4Cl at high pressures

Yurtseven, Hasan Hamit
Salihoglu, S.
Sen, S.
We predict in this study using the mean-field theory, the phase-line equation from the free energy expanded in terms of the order parameters of solid II and III phases of NH4Cl and ND4Cl close to the X-phase transitions at high pressures. Using the temperature and pressure dependence of the coefficients given in the phase-line equation, it is shown that the experimentally observed T-P phase diagram for the solid II-solid III transition, can be predicted from the mean field model studied here for both crystalline structures. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.