Inelastic neutron- and Raman-scattering studies of muscovite and vermiculite layered silicates

Abstract

Investigations on the lattice dynamics of muscovite and vermiculite have been carried out by inelastic neutron scattering and Raman scattering. In the neutron measurements, dispersion curves for the out-of-plane and in-plane LA and TA phonons were fully obtained for muscovite, while more limited data were obtained for Mg vermiculite. Sound velocities were estimated from the slopes of the dispersion curves. Raman-scattering experiments revealed an interlayer shearing mode in Na and Sr vermiculites in the 0-water-layer hydration state. The intercalated water molecules in Na and Sr vermiculites exhibited a broad Raman feature (OH stretching vibrations) at 3450 cm with a full width at half maximum of -300 cm '. In addition, relatively sharp Raman peaks from the inner-layer hydroxyls in the host octahedral layers were found at -3700 cm '. These peaks were sensitive to the hydration state or charge in the intercalated layer.

Moving Excitations in Cation Lattices

“…The maximum frequency in physical units is about 2.2 THz, which is larger than that obtained with molecular dynamics and neutron spectroscopy to be about 1.6 THz [24][25][26]. This is understandable due to the simplicity of our model considering just one type of atoms compared with the complexity of real mica, but it is within the same range of values.…”

Mechanisms and Crystal Chemistry of Oxidation in Annite: Resolving the Hydrogen-Loss and Vacancy Reactions

“…Pajcini and Dhamelincourt, 1994;Robert et al, 1989). It is also known that sorbed water is less Raman intense than structural OH bands, although intercalated water is easily measured in, for example, vermiculite (Wada and Kamitakahara, 1991). The intrinsic Raman preference for the N band that we observe may be a consequence of the fact that only the N band OH groups are aligned close to the c axis, in that Raman intensity depends on OH electric dipole moment to lattice vibration coupling, and lattice vibrations along c may be particularly easily induced by radiation-driven oscillations of c-aligned OH groups; relative to I band OH groups that are not aligned to specific crystallographic directions and that tend to lie closer to the stiffer ab plane.…”

Optimization of a label‐free biosensor vertically characterized based on a periodic lattice of high aspect ratio SU‐8 nano‐pillars with a simplified 2D theoretical model

“…The maximum frequency in physical units is about 2.2 THz which is larger than the one obtained with molecular dynamics and neutron spectroscopy of about 1.6 THz (Collins et al, 1993;Wada et al, 1991;Chaplot et al, 2002). This is understandable given the simplicity of our model taking into account just one type of atom compared with the complexity of real mica, but it is within the same range of values.…”