Publication

Modeling of the Raman spectrum of vitreous silica: concentration of small ring structures

Alfredo Pasquarello
2002
Journal Articles

Abstract

To calculate the Raman spectrum of vitreous silica, we use a model structure consisting of a disordered network of cornersharing tetrahedra, for which the vibrational frequencies and eigenmodes were obtained previously by first principles. The Raman cross-section is evaluated using a bond polarizability model with parameters derived from first-principles results for a-quartz. This model reproduces the major features of the spectrum. By comparing measured and calculated intensities of the defect lines D-1 and D-2, weestimate that similar to0.2% and similar to3% of oxygen atoms in vitreous silica belong to three- and four-membered rings, respectively. (C) 2002 Elsevier Science B.V. All rights reserved.

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https://infoscience.epfl.ch/entities/publication/9f44acdb-c539-44f5-988c-00bb6e358716

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Alfredo Pasquarello
2002
Journal Articles

Abstract

Official source

https://infoscience.epfl.ch/entities/publication/9f44acdb-c539-44f5-988c-00bb6e358716

About this result

Related concepts (32)

Raman spectroscopy

Raman spectroscopy (ˈrɑːmən) (named after Indian physicist C. V. Raman) is a spectroscopic technique typically used to determine vibrational modes of molecules, although rotational and other low-frequency modes of systems may also be observed. Raman spectroscopy is commonly used in chemistry to provide a structural fingerprint by which molecules can be identified. Raman spectroscopy relies upon inelastic scattering of photons, known as Raman scattering.

Raman scattering

Raman scattering or the Raman effect (ˈrɑːmən) is the inelastic scattering of photons by matter, meaning that there is both an exchange of energy and a change in the light's direction. Typically this effect involves vibrational energy being gained by a molecule as incident photons from a visible laser are shifted to lower energy. This is called normal Stokes Raman scattering. The effect is exploited by chemists and physicists to gain information about materials for a variety of purposes by performing various forms of Raman spectroscopy.

Resonance Raman spectroscopy

Resonance Raman spectroscopy (RR spectroscopy or RRS) is a variant of Raman spectroscopy in which the incident photon energy is close in energy to an electronic transition of a compound or material under examination. This similarity in energy (resonance) leads to greatly increased intensity of the Raman scattering of certain vibrational modes, compared to ordinary Raman spectroscopy. Resonance Raman spectroscopy has much greater sensitivity than non-resonance Raman spectroscopy, allowing for the analysis of compounds with inherently weak Raman scattering intensities, or at very low concentrations.

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Modeling of the Raman spectrum of vitreous silica: concentration of small ring structures

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