Single-crystal IR spectroscopy of strong hydrogen bonds in pectolite, NaCa2[Si3O8(OH)], and serandite, NaMn2[Si3O3(OH)]

Author(s): Vera M. F. Hammer, Eugen Libowitzky, George R. Rossman
Abstract: Polarized IR absorption spectra of thin, oriented single-crystal slabs of pectolite and serandite were recorded between 4000 and 350 cm-1 at 298 and 83 K. The spectra of both minerals show a broad absorption region parallel to the silicate chains (b direction) that is centered around 1000 cm-1, which is interrupted by a transmission window, and which is superimposed by sharp silicate, lattice, and overtone modes. This band is assigned to the OH stretching mode consistent with the alignment of the O-H ×××O hydrogen bond parallel to be and the short O×××O distance of 2.45-2.48 .ANG. that was found in previous X-ray structure refinements. At 1396 cm-1 (pectolite) and 1386 cm-1 (serandite) an OH bending mode is obsd. in the IR spectra parallel to c. At low temps., this mode shifts up to higher frequencies (1403 cm-1 at 83 K in pectolite), whereas the down-shift of the OH stretching mode cannot be obsd. due to the extremely broad band width. The slightly higher energy of the bending mode in pectolite indicates a slightly stronger hydrogen bond with respect to serandite. However, the bond length in serandite is slightly shorter than that in pectolite. An asym. O-H×××O bond is confirmed in pectolite and serandite through comparison with different materials with similar, very strong hydrogen bonds and low-energy OH stretching modes.
Organisation(s): Department of Mineralogy and Crystallography
External organisation(s): Naturhistorisches Museum Wien (NHM), California Institute of Technology (Caltech)
Journal: American Mineralogist: an international journal of earth and planetary materials
Volume: 83
Pages: 569-576
No. of pages: 8
ISSN: 0003-004X
Publication date: 05-1998
Peer reviewed: Yes
Austrian Fields of Science 2012: 105113 Crystallography, 105116 Mineralogy, 104026 Spectroscopy
Portal url: https://ucrisportal.univie.ac.at/en/publications/singlecrystal-ir-spectroscopy-of-strong-hydrogen-bonds-in-pectolite-naca2si3o8oh-and-serandite-namn2si3o3oh(4969c871-022c-4a3f-b1dc-48ba5750e328).html

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Single-crystal IR spectroscopy of strong hydrogen bonds in pectolite, NaCa<sub>2</sub>[Si<sub>3</sub>O<sub>8</sub>(OH)], and serandite, NaMn<sub>2</sub>[Si<sub>3</sub>O<sub>3</sub>(OH)]