| The temperature and concentration dependencies of thermodynamic functions for ferroelectric-antiferroelectric mixed systems are discussed. The model Hamiltonian describe both ferroelectric (site dipole momentum oriented in z-direction in crystal) and antiferroelectric (site dipole momentum oriented in x-direction) subsytems of mixed hydrogen bonded ferroelectrics of KDP type. In the second order of replicas expansion, the free energy and others thermodynamic functions are calculated. The conditions for different phases (para-, ferro-, antiferroelectric, dipole glass, and some mixed combinations of them) realization has been founded. The critical behaviour of thermodynamic functions and the crossover problem are discussed. |
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