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Pseudospin Hamiltonian parameters evaluated with regard to alkali metal ions in K 3 (H/D)(SO 4 ) 2 materials
Author(s) -
Dolin S. P.,
Levin A. A.,
Mikhailova T. Yu.,
Solin M. V.,
Gavriluyk A. B.,
Polyakov E. V.
Publication year - 2004
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.20411
Subject(s) - hamiltonian (control theory) , ion , alkali metal , quantum tunnelling , ising model , dimer , chemistry , ab initio , coupled cluster , perturbation theory (quantum mechanics) , quantum , coupling parameter , physics , condensed matter physics , quantum mechanics , molecule , nuclear magnetic resonance , mathematical optimization , mathematics
An analysis of ferroelectric behavior of K 3 (H/D)(SO 4 ) 2 as members of the M 3 (H/D)(AO 4 ) 2 family is examined quantum chemically in the cluster approach using the structural models extended through the incorporation of K ions in an explicit form. We apply several structural models that describe the different types of (H/D)(SO 4 ) 2 ‐dimer surrounded by K ions, the geometry of the dimer being borrowed from the corrected diffraction data of the K 3 D(SO 4 ) 2 crystal in its ordered phase at the temperature below critical point T c = 85 K. The calculations of the pseudospin Hamiltonian parameters—the Ising coupling parameters J ij and tunneling integrals Ω—were performed on the Hartree–Fock and second‐order Møller–Plesset perturbation theory levels with the 6‐31G–type basis sets. It is demonstrated that an effect of the K ions incorporation on the J ij values is minor (about several Kelvins). At the same time an influence of these ions on the double‐well potential characteristics (particularly, on the barrier heights) and thus on the tunneling integral value is more pronounced for both D‐ and H‐containing species. Despite the changes of the Hamiltonian parameters found, the major conclusion obtained earlier, referring to the suppression of the structural phase transition in H‐containing specimens due to proton quantum fluctuations, remains valid. The numerical estimations of the critical temperature T c for completely deuterated materials that are obtained with and without regard to alkali metal ions are discussed. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005