Vibrational analysis of the dioctahedral mica: 2M(1) muscovite

Raman spectra and lattice dynamics calculations are presented for the dioct ahedral mica, muscovite. Calculated fundamental mode frequencies for the Ra man-active and A(g) and B-g species were fit to observed fundamentals assig ned to features in the two polarized Raman spectra collected, so that unamb iguous vibrational assignments could be made to most peaks in the Raman dat a. Calculated frequencies for the IR-active A(u) and B-u modes generally fa ll within the frequency ranges of bands in the IR spectra for muscovite pre sented earlier. Factor group analysis indicates that motion from all atom t ypes in the muscovite structure can be found in modes for all four vibratio nal species. Force constant values determined for muscovite are similar to equivalent values calculated for the trioctahedral mica, phlogopite. Raman and IR-active modes calculated at frequencies greater than 800 cm(-1) are d ominated by internal sheet T-O stretch and T-O-T bend motions, where T is a tetrahedral site. Modes between 800 and 360 cm(-1) have internal tetrahedr al sheet motions mixed with K and octahedral Al displacements. Modes at fre quencies less than 360 cm(-1) have lattice and OH motions. Inter-sheet bond ing in the muscovite structure is strong enough to affect modes at frequenc ies as high as 824 cm(-1).