Interionic Vibrations and Glass Transitions in Ionic Oxide Metaphosphate Glasses.
BROWN UNIV PROVIDENCE R I DEPT OF CHEMISTRY
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The far infrared spectrum of each ionic metal-metaphosphate glass, MPO3n M Li, Na, K, Rb, Cs and MPO32n M Ca, Sr, Ba, contains a broad absorption band whose peak frequency and halfbandwidth are strongly dependent on the mass and charge of the glass-modifying cation. Each such band, which appears as the envelope of the optical phonon spectrum of the crystalline form of the material, is assigned to a density of coupled oscillator pseudo phonon states, which assignment is shown to be consistent with experimental linear variations of frequency with bandwidth. The net effect of coupling the oscillators in the vitreous disordered system is equivalently treated as a single damped harmonic oscillator. The damping coefficient is constant in each series as is the complex part of the refractive index. The force constant, the excitation quantum number, and mean square amplitudes are computed. It is shown that the energy required to pull the anion site away from the cation, permitting the glass transition to ensue, is a constant for each series of metaphosphate glasses.
- Atomic and Molecular Physics and Spectroscopy
- Solid State Physics