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Titolo:
MODEL OF QUADRUPOLAR GLASS OF MIXED-ALKALI CYANIDE CRYSTALS
Autore:
WALASEK K; LUKIERSKAWALASEK K;
Indirizzi:
PEDAGOG UNIV ZIELONA GORA,INST PHYS,PL SLOWIANSKI 6 PL-65065 ZIELONA GORA POLAND
Titolo Testata:
Physical review. B, Condensed matter
fascicolo: 17, volume: 48, anno: 1993,
pagine: 12550 - 12557
SICI:
0163-1829(1993)48:17<12550:MOQGOM>2.0.ZU;2-V
Fonte:
ISI
Lingua:
ENG
Soggetto:
ANOMALOUS THERMOELASTIC BEHAVIOR; PHASE-TRANSITIONS; MOLECULAR REORIENTATIONS; ELASTIC PROPERTIES; SOLID HYDROGEN; STATE; DYNAMICS; (KBR)1-X(KCN)X; (KCN)X(KBR)1-X; M(CN)XX1-X;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
29
Recensione:
Indirizzi per estratti:
Citazione:
K. Walasek e K. Lukierskawalasek, "MODEL OF QUADRUPOLAR GLASS OF MIXED-ALKALI CYANIDE CRYSTALS", Physical review. B, Condensed matter, 48(17), 1993, pp. 12550-12557

Abstract

A model of the transition from the orientationally disordered to the quadrupolar-glass (QG) phase of mixed alkali halide cyanide crystals is proposed. Starting from the semimicroscopic Hamiltonian constructed by Vollmayr, Kree, and Zippelius the effective Hamiltonian containing random long-ranged orientational interactions between CN- ions and their orientational coupling to the random local strain field has been obtained. The CN- ion is treated as a quadrupolar molecule and no restriction has been made to a finite number of spatial orientations of it. With the Sherrington-Kirkpatrick approach the formula for the free energy has been derived. In the framework of the replica-symmetric theorythe Landau expansion of the free energy up to third order in the QG Edwards-Anderson parameter has been performed in the absence of the random local strain field. This predicts a continuous QG transition. However, it is smeared out due to the influence of the random local strains, which in fact have a nonzero value. The elastic compliance has beencalculated and it has been shown, that T2g orientational modes governthe softening of the elastic constant C44 on approaching the QG transition point, whereas E2g modes are responsible for the much less pronounced temperature dependence of C-11 and C-12. This is in agreement with experimental data.

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Documento generato il 26/09/20 alle ore 08:44:49