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Full-Text Articles in Physical Sciences and Mathematics
Raman Scattering And Lattice-Dynamical Calculations Of Alkali-Metal Sulfates, D. Liu, H. M. Lu, John R. Hardy, F. G. Ullman
Raman Scattering And Lattice-Dynamical Calculations Of Alkali-Metal Sulfates, D. Liu, H. M. Lu, John R. Hardy, F. G. Ullman
John R. Hardy Papers
Raman-scattering measurements on single crystals of K2SO4, Rb2SO4, and Cs2SO4 have been made at both room and liquid-nitrogen temperatures. Lattice-dynamical calculations, based on a rigid-ion model using the Gordon-Kim method to calculate the short-range potentials, were performed. The influence of the alkali-metal ions on the lattice-dynamical properties of the crystals is discussed.
First-Principles Study Of Phase Transitions In Kno3, H. M. Lu, John R. Hardy
First-Principles Study Of Phase Transitions In Kno3, H. M. Lu, John R. Hardy
John R. Hardy Papers
We report a first-principles simulation study of phase transitions in KNO3, using our recently developed method for treating ionic molecular solids. With the interionic potentials calculated from ab initio electron charge densities of the ions, our structural static relaxation gave close fits to both the normal room-temperature (α-phase) and the ferroelectric (γ-phase) structures. Our supercell molecular-dynamics calculations closely simulated the transitions from the α phase and γ phase to the high-temperature disordered β phase, and successfully reproduced the abnormally large c-axis thermal expansion observed in experiment. Both transitions were found to be initiated by the rotations of the …
First-Principles Study Of The Lattice Dynamics Of K2So4, D. Liu, H. M. Lu, F. G. Ullman, John R. Hardy
First-Principles Study Of The Lattice Dynamics Of K2So4, D. Liu, H. M. Lu, F. G. Ullman, John R. Hardy
John R. Hardy Papers
Using a newly developed first-principles approach to simulations of ionic molecular crystals, we performed static relaxation, molecular-dynamics simulation, and lattice-dynamics calculations, and measurements of the Raman spectrum, for the Pnam structure of K2SO4. It was found that the structure does not have the zone-center instability present in isomorphous K2SeO42 found in an earlier study. This difference between the two systems is attributed to the different charge distributions in the molecular ions. The calculated Raman-active zone-center frequencies for the Pnam structure of K2SO4 were found to be in general agreement with …