Relaxation times and ergodic properties in a realistic ionic-crystal model, and the modern form of the FPU problem

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.

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Elastic constants of polycrystalline Y1Ba2Cu3Ox

Journal of Materials Research ◽

10.1557/jmr.1992.2905 ◽

1992 ◽

Vol 7 (11) ◽

pp. 2905-2907 ◽

Cited By ~ 18

Author(s):

Hassel Ledbetter

Keyword(s):

Grain Boundary ◽

Bulk Modulus ◽

Debye Temperature ◽

Oxygen Content ◽

Elastic Constants ◽

Model Prediction ◽

Ionic Crystal ◽

Poisson Ratio ◽

Young’S Moduli ◽

Crystal Model

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.

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Critical TemperaturesTcof Ionic-Crystal Model for Infinite-Layer Compounds

Journal of the Physical Society of Japan ◽

10.1143/jpsj.61.4663 ◽

1992 ◽

Vol 61 (12) ◽

pp. 4663-4664 ◽

Cited By ~ 3

Author(s):

Chikao Kawabata ◽

Takamitsu Nakanishi

Keyword(s):

Ionic Crystal ◽

Infinite Layer ◽

Crystal Model

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The Nonempirical Calculation of the Cation Ordering and Lattice Dynamics in the Solid Solutions of PbSc1/2Nb1/2O3 and PbSc1/2Ta1/2O3

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.115.305 ◽

2006 ◽

Vol 115 ◽

pp. 305-310

Author(s):

V.I. Zinenko ◽

S.N. Sofronova

Keyword(s):

Solid Solutions ◽

Ionic Crystal ◽

Mean Field ◽

Nonempirical Calculation ◽

Cation Ordering ◽

Effective Hamiltonian ◽

The Monte Carlo Method ◽

Ordered Phases ◽

Phase Transition Temperatures ◽

Crystal Model

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.

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An emerging technology: Nuclear magnetic resonance microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010010706x ◽

1988 ◽

Vol 46 ◽

pp. 1000-1001

Author(s):

M.J. Hennessy ◽

E. Kwok

Keyword(s):

Nuclear Magnetic Resonance ◽

Magnetic Resonance ◽

Relaxation Times ◽

Basic Research ◽

Local Environment ◽

Magnetic Resonance Images ◽

Nmr Microscopy ◽

Mri Scans ◽

Temperature Relaxation ◽

Nuclear Magnetic

Much progress in nuclear magnetic resonance microscope has been made in the last few years as a result of improved instrumentation and techniques being made available through basic research in magnetic resonance imaging (MRI) technologies for medicine. Nuclear magnetic resonance (NMR) was first observed in the hydrogen nucleus in water by Bloch, Purcell and Pound over 40 years ago. Today, in medicine, virtually all commercial MRI scans are made of water bound in tissue. This is also true for NMR microscopy, which has focussed mainly on biological applications. The reason water is the favored molecule for NMR is because water is,the most abundant molecule in biology. It is also the most NMR sensitive having the largest nuclear magnetic moment and having reasonable room temperature relaxation times (from 10 ms to 3 sec). The contrast seen in magnetic resonance images is due mostly to distribution of water relaxation times in sample which are extremely sensitive to the local environment.

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