Origin of the high-frequency doublet in the vibrational spectrum of vitreous SiO2

Johannes Sarnthein, Alfredo Pasquarello, Roberto Car

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Abstract

The vibrational properties of amorphous SiO2 were studied within first- principles density functional theory. The calculated spectrum is in good agreement with neutron data, showing, in particular, a double peak in the high-frequency region. This doublet results from different local modes of the tetrahedral subunits and cannot be ascribed to a longitudinal-optic- transverse-optic (LO-TO) effect. This solves a long-standing controversy about the origin of the doublet in neutron spectra. A LO-TO splitting is recovered only when the long-wavelength limit is probed, as in optical experiments. These findings should be a general feature of tetrahedral AX2 amorphous networks.

Original languageEnglish (US)
Pages (from-to)1925-1927
Number of pages3
JournalScience
Volume275
Issue number5308
DOIs
StatePublished - Mar 28 1997
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • General

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