Vibrational states in opals revisited
Ivanov, Viacheslav Grigorevich, Reyes, B. Aguilar, Fritsch, E. and Faulques, Eric. (2011) Vibrational states in opals revisited. The Journal of Physical Chemistry Part C: Nanomaterials, Interfaces and Hard Matter, Vol.115 (No.24). pp. 11968-11975. ISSN 1932-7447Full text not available from this repository.
Official URL: http://dx.doi.org/10.1021/jp2027115
Quantitative assessment of the vibrational features of nanocrystalline hydrated silicas is still not yet ascertained, although this is a relevant issue in silica physics. In this work, we examine the vibrational states in two generic opaline silicas. PM3 semiempirical calculations on finite SiO(2) hydrated clusters prove that the low-frequency Raman lines experimentally observed at similar to 307, 340, and 370 cm(-1) and the high-frequency ones at 790 cm(-1) and 1080 cm(-1) stem from O-Si-O bending vibrations in six-membered rings of corner-shared SiO(4) tetrahedra and O-Si-O symmetric/asymmetric stretch vibrations, respectively. Lattice dynamical calculations on crystalline silica polymorphs show that the predominance of tridymite over cristobalite in opaline silicas cannot be established due to the intrinsic nanoscale crystalline order of the materials. We conclude that the vibrational variations observed between opaline silicas are due to gradual formations of six-membered rings in a disordered SiO(2) matrix.
|Item Type:||Journal Article|
|Subjects:||Q Science > QC Physics|
|Divisions:||Faculty of Science > Physics|
|Library of Congress Subject Headings (LCSH):||Vibrational spectra, Opals|
|Journal or Publication Title:||The Journal of Physical Chemistry Part C: Nanomaterials, Interfaces and Hard Matter|
|Publisher:||American Chemical Society|
|Page Range:||pp. 11968-11975|
|Funder:||North Atlantic Treaty Organization (NATO)|
|Grant number:||PST. CLG.979685 (NATO), PAI-RILA No. 09839SD (NATO), PICS CNRS-NASU No. 4766 (2008-2011) (NATO)|
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