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The crystal structures of Ba2R2/3V2O8 (R = La, Nd) and Sr2La2/3V2O8; palmierite derivatives (2000)

Skakle, J. M. S. ; Coats, A. M. ; Marr, J.

Springer

Journal of materials science 35 (2000), S. 3251-3256

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ISSN: 1573-4803

Source: Springer Online Journal Archives 1860-2000

Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: Abstract The title phases Ba2R2/3V2O8 (R = La, Nd) and Sr2La2/3V2O8, synthesised by solid state reaction of oxides at 1350°C, have structures derived from that of the palmierite-type of Ba3V2O8; the stoichiometry is often written as A3RV3O12. Ba2La2/3V2O8 is hexagonal, spacegroup R―3m, a = 5.75271(7), c = 21.0473(5) Å, Z = 3; cation ordering was determined by joint Rietveld refinement using X-ray and neutron powder diffraction data, R wp = 4.45%, R p = 6.33%, χ2 = 6.847. In the Ba3V2O8 structure, Ba occupies two sites: 3a and 6c. In Ba2La2/3V2O8, Ba wholly occupies the 3a site; the 6c site contains both Ba, La and vacancies. Bond valence analysis was inconclusive, but tends to support the presence of Ba on the 3a site. Sr2La2/3V2O8 and Ba2Nd2/3V2O8 are isostructural, as confirmed by Rietveld refinement using X-ray powder diffraction data. Ba2R2/3V2O8 phases could not be synthesised for lanthanides, R, smaller than Sm.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1004815120209

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Raman and infrared intensities in trimethylamine species, polarizability and dipole derivatives and effective charges (1995)

Murphy, W. F. ; McKean, D. C. ; Coats, A. M. ; [et al.]

Chichester [u.a.] : Wiley-Blackwell

Journal of Raman Spectroscopy 26 (1995), S. 763-770

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ISSN: 0377-0486

Keywords: Chemistry ; Analytical Chemistry and Spectroscopy

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Physics

Notes: Raman trace scattering intensities are reported for the d0, d3, d6, d8 and d9 deuterated species of trimethylamine. Using normal coordinates from a previous scaled ab initio force field, the data are analysed in terms of seven derivatives ∂α¯∂S in the A1 symmetry species, each of which is well defined. Similar derivatives (dα¯/dr)CH with respect to the stretching of the two kinds of CH bond are shown to be very different from each other, showing a marked effect of the lone pair. Infrared intensities were measured for the d0, d8 and d9 species. These are well reproduced by ab initio calculations at the MP2/6-31G* level. The dipole derivative for the CHS bond trans to the lone pair is much greater than that for the Ha bond in the gauche position. The ab initio atomic polar tensors were used to obtain effective charges and other invariants, and the directions of dμ/dr for the CH bonds were determined. That for the Hs bond lies 23° off the bond direction. The ratio Xa/Xs of the abundances of the Ha and Hs conformers in the d8 isotopomer, required for the above analyses of the spectra, is calculated to be 1.80(4).

Additional Material: 2 Ill.