A high-temperature Fourier transform infrared study of the interlayer and Si–O-stretching region in phengite-2M₁

Abstract

A natural phengite-2M1 of composition (K0.95Na0.05)(Al0.76Fe0.14Mg0.10)2 (Si3.25Al0.75)O10(OH1.96F0.04) [a= 5.2173(1) Å, b= 9.0493(2) Å, c= 19.989 (1) Å and β = 95.734(4)°] was studied using in situ high-temperature FTIR. Correlations to structural changes were made using previously-reported neutron diffraction data from the same sample. Correlations have been made between the microscopic atomic displacements (arising from thermal effects) and analogous macroscopic properties, such as bond strain and ditrigonal distortions. Spectra were collected in the far-infrared region to study the behaviour of the interlayer (K+) cation and also in the mid-infrared region to distinguish the Si–O stretching modes. We found anisotropic thermal expansion of the interlayer site. The K O bond length is divided into K Oouter and K Oinner, and the K–Oinner bond length is correlated with the far-infrared spectra. The thermal dependence of the correlation between K–O bond length and corresponding far-infrared stretching frequency is different from the effect of the chemical composition. We also found that the K–O bond strain could be successfully resolved into the sum of inner strain and lattice strain. The Si–O stretching mode, obtained from the mid-infrared measurements, showed only weak changes. However, the neutron refinement data showed different thermal behaviour for distinct crystallographic T-sites.

Stability of lanthanum-saturated montmorillonite under high pressure and high temperature conditions

“…The spectra obtained at all pressures were very similar, with the exception of the peak at 1040 cm − 1 (Fig. 3), which corresponds to the tetrahedral Si\O bond (Mookherjee and Redfern, 2002); this peak shifted from 1039 cm − 1 at atmospheric pressure to 1063 cm − 1 at 12 GPa. The change in this bond frequency from lower to higher frequency with increasing pressure was also observed by Alabarse et al (2011) for Ca 2+ -Mt and is related to the approach of the Si\O apical bond from the tetrahedron, which increases its vibrational modes.…”

“…2). The band between 3000 and 3600 cm −1 corresponds to the hydroxyl groups in the octahedral and interlayer water of both Ca 2+ -and La 3+ -montmorillonite (Mookherjee and Redfern, 2002;Aranha, 2007). Peaks at 848 and 916 cm −1 due to Al\OH\Al bonding, characteristic of montmorillonite with a high amount of Al (Wagner et al, 1994), are present in both the Ca 2+ -and La 3+ -Mt spectra.…”

Computational study of the elastic behavior of the 2M1 muscovite-paragonite series

“…With increasing substitution, ∆<X⋅⋅⋅O> and their slopes are larger in Na + than in K + cavities. These variations could be due to the fitting of the cavities to the Sidorenko et al (1977); Flux86 = values from Flux and Chatterjee (1986); Gug87 = values from Guggenheim et al (1987); Cat89/94 = values from Catti et al (1989) and Catti et al (1994); Roux96 = values from Roux and Hovis (1996); Com97 = values from Comodi and Zanazzi (1997); Bri98 = values from AG1 and/or RA1 and/or C3-29b samples from Brigatti et al (1998); and Moo02 = values from Mookherjee and Redfern (2002 …”

High-pressure behavior of 2M1 muscovite

“…The first region shows a linear modulus of 264 GPa; the second region shows a linear modulus of some 92 GPa; and the third region shows a linear modulus of 353 GPa. Mookherjee and redfern (2002) have used the difference of the quadratic interatomic distances [d 2…”