Thermal fluctuations in a realistic ionic-crystal model

2022 ◽  
Vol 586 ◽  
pp. 126463
Author(s):  
Fabrizio Gangemi ◽  
Roberto Gangemi ◽  
Andrea Carati ◽  
Luigi Galgani
2020 ◽  
Vol 229 (5) ◽  
pp. 743-749
Author(s):  
Andrea Carati ◽  
Luigi Galgani ◽  
Fabrizio Gangemi ◽  
Roberto Gangemi

1990 ◽  
Vol 5 (2) ◽  
pp. 241-244 ◽  
Author(s):  
Hassel Ledbetter ◽  
Ming Lei

Using several measured and calculated physical properties, we argue that the high-Tc metal-oxide superconductor Y1Ba2Cu3O7 is elastically soft compared with BaTiO3 or SrTiO3. We conclude that the bulk modulus equals approximately 107 GPa, despite several high-pressure x-ray diffraction studies that report values up to approximately 200 GPa. Part of the argument uses an ionic-crystal-model calculation of the bulk modulus.


1992 ◽  
Vol 7 (11) ◽  
pp. 2905-2907 ◽  
Author(s):  
Hassel Ledbetter

We measured the elastic constants of polycrystalline Y1Ba2Cu3Ox with eleven oxygen contents varying from 6.2 to 6.9. Reported properties include sound velocities; bulk, shear, Young's moduli; Poisson ratio; Debye temperature. After correction to the void-free state, the measurements fail to show a systematic dependence on oxygen content. Focusing on the bulk modulus, all measurements fall below an ionic-crystal model prediction, by 5–50%. We attribute this macroscopic softness to either microcracks or weak grain-boundary mechanical linkages. For the case x = 6.9, we suggest a set of intrinsic elastic constants.


1992 ◽  
Vol 61 (12) ◽  
pp. 4663-4664 ◽  
Author(s):  
Chikao Kawabata ◽  
Takamitsu Nakanishi

2008 ◽  
Vol 78 (3) ◽  
Author(s):  
J. A. P. Ramos ◽  
E. Granato ◽  
C. V. Achim ◽  
S. C. Ying ◽  
K. R. Elder ◽  
...  

1989 ◽  
Vol 03 (15) ◽  
pp. 1121-1126 ◽  
Author(s):  
LEI-HAN TANG

The phason elasticity of random tiling and quasiperiodic crystal models is discussed. Long-wavelength phasons in the random tiling model are described by a square-gradient free energy of entropic origin. In the quasiperiodic crystal model, thermal fluctuations lead to a transition from the zero temperature singular linear phason elastic energy to a quadratic phason elastic energy at high temperatures.


2006 ◽  
Vol 115 ◽  
pp. 305-310
Author(s):  
V.I. Zinenko ◽  
S.N. Sofronova

An effective Hamiltonian for the study of Sc–Nb(Ta) cation ordering in PbSc1/2Nb(Ta)1/2O3 solid solutions is worked out. To determine the parameters of the effective Hamiltonian, a nonempirical calculation is performed within an ionic-crystal model taking into account the deformation, dipole, and quadrupole polarizabilities of ions. The phase transition temperatures are calculated by the mean field, the cluster approximations, and the Monte-Carlo method. Within the same ionic-crystal model, we calculated the high-frequency permittivity, Born dynamic charges, and the phonon spectrum for completely disordered and ordered phases.


1986 ◽  
Vol 47 (6) ◽  
pp. 1029-1034 ◽  
Author(s):  
J.C. Parlebas ◽  
R.H. Victora ◽  
L.M. Falicov

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