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Full-Text Articles in Physics
Raman Spectrum Of Gadolinium Molybdate Above And Below The Ferroelectric Transition, Frank Ullman, B. J. Holden, B. N. Ganguly, John R. Hardy
Raman Spectrum Of Gadolinium Molybdate Above And Below The Ferroelectric Transition, Frank Ullman, B. J. Holden, B. N. Ganguly, John R. Hardy
John R. Hardy Papers
90 °-scattered Raman spectra of single-domain gadolinium molybdate have been obtained at room temperature and above the 159 °C ferroelectric transition on several crystal orientations. Lines in the 0-200-cm-1 range can all be associated with Raman-active phonons and are identified by symmetry considerations, scattering-efficiency calculations, and comparison of spectra for different crystal orientations. Lines in the 200-1000-cm-1 range can be identified with coupled vibrations of tetrahedral molybdate ions. Spectra for frequencies above 1000 cm-1 originate from impurity flourescence. The effect of the presence of multiple domains on the spectra was determined; the observed differences between single-domain and …
Lattice Dynamics Of A Rigid-Ion Model For Gadolinium Molybdate, L. L. Boyer, John R. Hardy
Lattice Dynamics Of A Rigid-Ion Model For Gadolinium Molybdate, L. L. Boyer, John R. Hardy
John R. Hardy Papers
Results of lattice-dynamical calculations are presented which support the view that the ferroelectric phase transition in gadolinium molybdate (GMO) arises from the softening and ultimate instability of a doubly degenerate zone-edge mode of the high-temperature paraelectric phase. We have used a rigid-ion model in which the short-range force constants are obtained from a detailed knowledge of the crystal structure together with the conditions imposed by the requirement that the crystal must be in static equilibrium under the combined influence of both Coulomb and short-range forces. Our results show that this type of approach is very useful when one is dealing …
Static Equilibrium Conditions For A Rigid-Ion Crystal, L. L. Boyer, John R. Hardy
Static Equilibrium Conditions For A Rigid-Ion Crystal, L. L. Boyer, John R. Hardy
John R. Hardy Papers
The equilibrium requirements for a static ionic crystal impose a number of constraints on the short-range forces which become increasingly more important when one is dealing with complex structures. These constraints are presented and discussed for a general rigid-ion lattice, and a specific discussion is presented for the wurtzite structure.
Determination Of The Origin Of The 10.6-Pm Absorption In C02 Laser Window Materials, John R. Hardy, B. S. Agrawal
Determination Of The Origin Of The 10.6-Pm Absorption In C02 Laser Window Materials, John R. Hardy, B. S. Agrawal
John R. Hardy Papers
Theoretical studies are presented which show that it should be possible to determine whether the absorption at 10.6 pm in alkali halides is due to impurities or whether it is intrinsic. These studies show that the temperature dependence of the measured absorption should be very different for intrinsic multiphonon absorption as compared with defect-activated absorption.