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Full-Text Articles in Physics
Arnold M. Karo, John R. Creighton, John R. Hiskes, Fredrick Mcmurphy, John R. Hardy
Arnold M. Karo, John R. Creighton, John R. Hiskes, Fredrick Mcmurphy, John R. Hardy
John R. Hardy Papers
Arnold M. Karo died on 16 June 1991 at age 63, after a yearlong battle with leukemia. He was a theoretical chemist and solid-state physicist with the chemistry and materials science department at Lawrence Livermore National Laboratory.
Phase Transitions In K2Zncl4, H. M. Lu, John R. Hardy
Phase Transitions In K2Zncl4, H. M. Lu, John R. Hardy
John R. Hardy Papers
It is shown that the potential-energy surface in K2ZnCl4 contains a double-well structure, very similar to some of the other A2BX4 compounds (e.g., K2SeO4, Rb2ZnCl4), except that the double well is much deeper and broader, giving rise to a highly disordered high-temperature phase as observed experimentally. A lattice-dynamics study of the Pna21 structure shows an instability with the wave vector q=0.5b*+(0.5±δ)c*, providing an explanation to the incommensurate phase transition reported recently.
Raman Scattering And Lattice-Dynamical Calculations Of Crystalline Kno3, D. Liu, F. G. Ullman, John R. Hardy
Raman Scattering And Lattice-Dynamical Calculations Of Crystalline Kno3, D. Liu, F. G. Ullman, John R. Hardy
John R. Hardy Papers
The Raman spectrum of a KNO3 single crystal was measured at both room and liquid-nitrogen temperatures. Lattice-dynamical calculations, based on the rigid-ion approximation and empirical potentials, were performed. The possibility of a phase transition at 217 K was investigated by measuring the temperature dependence of the Raman spectrum.
Fractal Character Of Two-Dimensional Fluid Mixing At Both Continuum And Atomic Levels, H. Z. Cao, John Hardy, R. W. Douglass, P. T. Dawkins, Steven Dunbar
Fractal Character Of Two-Dimensional Fluid Mixing At Both Continuum And Atomic Levels, H. Z. Cao, John Hardy, R. W. Douglass, P. T. Dawkins, Steven Dunbar
John R. Hardy Papers
Studies in two dimensions have been made of the evolution of an initially linear interface between two liquid areas by both continuum hydrodynamics and molecular dynamics. It was found that at both levels the interface evolves into a fractal curve. While the limiting fractal dimensionalities (D) of the continuum and molecular interfaces differ, this difference is no greater than that that can be induced in the hydrodynamic results by marked changes in the initial conditions and/or fluid parameters. There is, however, a marked qualitative difference in the initial values of D. This is discussed and shown to …
Simulations Of Phase Transitions In Rb2Zncl4, H. M. Lu, John R. Hardy
Simulations Of Phase Transitions In Rb2Zncl4, H. M. Lu, John R. Hardy
John R. Hardy Papers
Structural relaxations, molecular-dynamics simulations, and lattice-dynamics calculations were performed to study the phase transitions in Rb2ZnCl4, using intermolecular and intramolecular potentials generated from ab initio quantum-chemistry calculations for the whole molecular ion ZnCl4 2-. Compared with an earlier treatment of the system by a polarizable-ion model, the present approach emphasizes the static effect of the electron covalency within the molecular ions that affects strongly both the intermolecular and intramolecular interactions. The calculations gave a close agreement with experiment on the static structures of the Pnam and the Pna21 phases and the transition …
Raman Scattering And Lattice-Dynamical Calculations Of Crystalline Kno3, H. M. Lu
Raman Scattering And Lattice-Dynamical Calculations Of Crystalline Kno3, H. M. Lu
John R. Hardy Papers
The Raman spectrum of a KNO3 single crystal was measured at both room and liquid-nitrogen temperatures. Lattice-dynamical calculations, based on the rigid-ion approximation and empirical potentials, were performed. The possibility of a phase transition at 217 K was investigated by measuring the temperature dependence of the Raman spectrum.
Lattice- And Molecular-Dynamics Studies Of Phase Transitions In Csliso4, V. Katkanant
Lattice- And Molecular-Dynamics Studies Of Phase Transitions In Csliso4, V. Katkanant
John R. Hardy Papers
We report results of a simulation of the phase transitions in CsLiSO4. These are based on our previously developed method for calculating parameter-free potential-energy surface for ionic molecular crystals. Our lattice-dynamical and molecular-dynamics studies show that the roomtemperature (Pnam) phase is unstable and transforms to the observed low-temperature (P1121/n) phase over approximately 200–280 K. The unstable modes of the Pnam phase have maximum instability at the zone center, which indicates a possible phase transformation without a cell multiplication. The rotational ordering of tetrahedral SOM4 2- was found to be …