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Titolo:
SECONDARY RELAXATIONS AND THE CONSTANT DENSITY OF SLATES IN QUADRUPOLAR GLASSES
Autore:
SOLF MP; KLEIN MW;
Indirizzi:
WORCESTER POLYTECH INST,DEPT PHYS,100 INST RD WORCESTER MA 01609 ROME LAB BEDFORD MA 01731
Titolo Testata:
Journal of non-crystalline solids
, volume: 172, anno: 1994,
parte:, 1
pagine: 531 - 537
SICI:
0022-3093(1994)172:<531:SRATCD>2.0.ZU;2-C
Fonte:
ISI
Lingua:
ENG
Soggetto:
ORIENTATIONALLY DISORDERED CRYSTALS; LOW-TEMPERATURE PROPERTIES; LOW-ENERGY EXCITATIONS; MIXED-CRYSTALS; STATE; (KBR)1-X(KCN)X; M(CN)XX1-X; (NACN)1-X(KCN)X; REORIENTATIONS; BEHAVIOR;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
32
Recensione:
Indirizzi per estratti:
Citazione:
M.P. Solf e M.W. Klein, "SECONDARY RELAXATIONS AND THE CONSTANT DENSITY OF SLATES IN QUADRUPOLAR GLASSES", Journal of non-crystalline solids, 172, 1994, pp. 531-537

Abstract

The Hamiltonian for a set of interacting quadrupoles (QPs) randomly distributed in a non-polar host is considered. One such system is (KCN)(x)(KBr)(1-x), where x denotes the fractional concentration of the CN(-)QPs; x is assumed to be in the regime where KCN-KBr exhibits glass-like properties, i.e., 0.2 less than or similar to x less than or similar to 0.6. The model Hamiltonian considers the QP-QP interaction between the CN- QPs and the interaction of CN- with elastic random fields caused by random fluctuations in the local environment of the CN- ions. For low temperatures, T, we assume that QPs freeze into a state of quenched orientational disorder. However, the ground state of a system of N interacting QPs is still 2(N)-fold degenerate. A perturbation approach is used to lift the degeneracy and it is shown that the QPs can be described in terms of an effective two-level system Hamiltonian and that the density of states for low energies is constant. The constant density arises from 180 degrees tunneling QPs coupled with a center ofmass displacement of the QPs and is not related to the electric dipole moment of CN-, as was suggested previously by Sethna et al.

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Documento generato il 27/10/20 alle ore 11:03:58