Statistical Theory for Displacement Ferroelectrics. II. Specific-Heat and Soft-Mode-Frequency Calculations

1969 ◽  
Vol 177 (2) ◽  
pp. 812-818 ◽  
Author(s):  
M. E. Lines
Keyword(s):  
Statistical Theory ◽  
Specific Heat ◽  
Soft Mode ◽  
Mode Frequency

scholarly journals Statistical theory of superlattices

1935 ◽  
Vol 150 (871) ◽  
pp. 552-575 ◽  
Keyword(s):  
Mathematical Method ◽  
Statistical Theory ◽  
Specific Heat ◽  
Low Temperatures ◽  
Lattice Points ◽  
The Other ◽  
Electric Resistance ◽  
Regular Lattice ◽  
Small Temperature ◽  
Average State

In a recent paper, Bragg and Williams have pointed out that the arrangement of the atoms in an alloy depends in a striking way on the temperature. At high temperatures, the atoms are distributed practically at random among the lattice points of the crystal, but at low temperatures a superlattice may be formed such that the atoms of one kind are arranged in a regular lattice of their own and the atoms of the other kind occupy the remaining “sites” in the crystal. The transition from the ordered to the disordered state occurs in a fairly small temperature range, and is accompanied by a large specific heat, an increase in electric resistance, etc. The mathematical method employed by Bragg and Williams is similar to that used in Weiss’s theory of ferromagnetism . Both involve the assumption that the “force” tending to produce order at a given point is uniquely determined by the average state of order throughout the crystal. Actually it will depend on the configuration of the atoms in the immediate neighbourhood of the point under consideration. The order of the crystal as a whole determines this configuration only on the average. In the present paper, the effect of fluctuations in configuration, which was neglected by Bragg and Williams, will be taken into account.

Magnetic-field dependence of the soft-mode frequency in KTa03AT 20K

1982 ◽  
Vol 44 (1) ◽  
pp. 121-128 ◽  
Author(s):  
W. N. Lawless ◽  
C. F. Clark ◽  
S. L. Swartz
Keyword(s):  
Magnetic Field ◽  
Field Dependence ◽  
Magnetic Field Dependence ◽  
Soft Mode ◽  
Mode Frequency

STABILISATION OF PARAELECTRIC PHASE BY STRONG CUBIC AND QUARTIC PHONON ANHARMONICITIES IN KDP CRYSTAL

1995 ◽  
Vol 09 (01) ◽  
pp. 45-55 ◽  
Author(s):  
T.C. UPADHYAY ◽  
N.S. PANWAR ◽  
B S. SEMWAL
Keyword(s):  
Soft Mode ◽  
Mode Frequency ◽  
Dielectric Susceptibility ◽  
Tangent Loss ◽  
Kdp Crystal ◽  
Coupled Mode ◽  
Para Phase ◽  
Real Value ◽  
Double Time ◽  
Anharmonic Interactions

Considering cubic and quartic phonon anharmonic interactions into the pseudospinphonon coupled mode model of Kobayashi6 expressions for shift, width, soft mode frequency and hence Curie temperature, dielectric susceptibility, Curie-Weiss constant and dielectric (tangent) loss have been evaluated for ferroelectric KDP. The method of retarded double-time thermal Green’s function and the treatment of Dyson’s equation have been used in the development. It is shown that cubic and quartic phonon anharmonic interactions render real value to the soft mode frequency in the para-phase. Results are in agreement with the experimental results of others.

Temperature Dependence of Soft Mode Frequency and Dielectric Constant in Ferroelectric PbHPO[sub 4] Crystal

2011 ◽  
Author(s):  
Trilok Chandra Upadhayay ◽  
Mayank Joshi ◽  
P. K. Bajpai ◽  
K. S. Ojha ◽  
K. N. Singh
Keyword(s):  
Dielectric Constant ◽  
Temperature Dependence ◽  
Soft Mode ◽  
Mode Frequency

Specific Heat of Synthetic High Polymers. I. A Study of Polyethylene Including a Statistical Theory of Crystallite Length

1952 ◽  
Vol 20 (5) ◽  
pp. 781-790 ◽  
Author(s):  
Malcolm Dole ◽  
W. P. Hettinger ◽  
N. R. Larson ◽  
J. A. Wethington
Keyword(s):  
Statistical Theory ◽  
Specific Heat ◽  
High Polymers

Variation of the soft-mode frequency in ferroelectric semiconductors in a static electric field

1988 ◽  
Vol 31 (1) ◽  
pp. 29-33
Author(s):  
G. M. Benkin ◽  
V. V. Zil'berberg ◽  
N. V. Shchedrina
Keyword(s):  
Electric Field ◽  
Soft Mode ◽  
Mode Frequency ◽  
Static Electric Field
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