| 1. |
- Eriksson, Anders, et al.
(författare)
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The use of spectroscopic data in the least-squares refinement of diffraction-obtained structure parameters. An example : K 2C 2O 4.H 2O
- 1982
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Ingår i: Acta Crystallogr. A, Cryst. Phys. Diffr. Theor. Gen. Crystallogr. (Denmark). - 0567-7394. ; A38, s. 138-142
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Tidskriftsartikel (refereegranskat)abstract
- A method is presented in which parameters obtained from vibrational spectroscopy are used in the least-squares refinement of positional and thermal parameters obtained from diffraction data. The method involves the calculation of those contributions to the temperature factors not well described by the second-rank tensor approximation conventionally used in crystal structure determinations. Expressions are given for the temperature-factor contributions from vibrational motion on an arc and from anharmonic linear motion. The method is applied to the water molecule in dipotassium oxalate monohydrate, 2K +.C 2O 4-.H 2O. Refinements using vibrational data are compared with a conventional refinement; the latter are shown to give considerable systematic errors in the geometrical parameters for the water molecule.
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| 2. |
- Hermansson, Kersti, et al.
(författare)
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Deformation electron density of lithium nitrate trihydrate, LiNO 3.3H 2O, at 120 and 295K
- 1984
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Ingår i: Acta Crystallographica Section C. - 0108-2701 .- 1600-5759. ; C40, s. 341-342
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Tidskriftsartikel (refereegranskat)abstract
- Mr=123.00, orthorhombic, Cmcm, Z=4; at 120K, a=6.713 (7), b=12.669 (4), c=5.968 (5) Aring, V=507.7 (7) Aring 3; at 295K, a=6.8018 (4), b=12.7132 (9), c=5.9990 (4), V=518.75 (6) Aring 3; m.p.=303.1K, Dx=1.575 g cm -3 (295K), f(000)=256; X-ray data (Mo Kalpha, lambda=0.71069 Aring) have been collected at 120K; final wR( F2) values 0.064 from conventional spherical-atom refinement and 0.033 from deformation refinement. The deformation electron density of LiNO 3.3H 2O has been studied at 120K (new data) and 295K in order to compare static and dynamic deformation maps derived at two temperatures. A combination of X-ray and neutron data has been used both for the X- N and the multipolar expansion maps. The N-O bond peaks are elongated perpendicular to the molecular plane. The water molecules show well developed deformation features and the hydrogen-bond density is consistent with what is usually observed for medium-strong hydrogen bonds.
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| 3. |
- Hermansson, Kersti, et al.
(författare)
-
The structure and electron deformation density of LiNO 2.H 2O at 295K
- 1983
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Ingår i: Acta Crystallographica Section C. - 0108-2701 .- 1600-5759. ; C39, s. 930-936
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Tidskriftsartikel (refereegranskat)abstract
- Mr=70.959, monoclinic, P2 1/ c, Z=4, a=3.3387 (3), b=14.2980 (10), c=6.3961 (5) Aring, beta=105.10 (1)deg, V=294.79 (4) Aring 3, Dx=1.60 Mg m -3, Mo Kalpha, lambda=0.71069 Aring, mu calc=0.154 mm -1, T=295 K, F(000)=144. Two data sets were collected out to sintheta/lambda=0.91 Aring -1: one on a twinned crystal, the other on a single crystal. Positional and thermal parameters from the two data sets show only random deviations. Somewhat high Rw( F2) values of 0.084 and 0.081, respectively, resulted from the refinement of a spherical-atom model. This reflects the inadequacies of such a model. Introduction of multipolar deformation functions for the single-crystal data set brought the Rw( F2) value down to 0.029. The crystal contains one independent Li + ion with fivefold coordination, a tetrahedrally coordinated H 2O molecule and an NO 2- ion which accepts two medium-strength hydrogen bonds [O-H...O 2.755 (1); O-H...N 2.890 (1) Aring] and has three Li +-O contacts. The static deformation density for the NO 2- ion shows N-O bond maxima of 0.50 e Aring -3; O lone-pair maxima of 0.20-0.30 e Aring -3 are situated in the molecular planes at approximately 90deg to the N-O bonds. The lone-pair density associated with the water O is markedly asymmetric; no support for this effect has been found in theoretical model calculations, however.
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| 4. |
- Lannefors, Hans O., et al.
(författare)
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Interelement and Multi-Station Concentration Evidence for Large Scale Aerosol Sulfur Transport across Sweden
- 1980
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Ingår i: Tellus, Series A: Dynamic Meteorology and Oceanography. - : Stockholm University Press. - 0280-6495. ; 32:6, s. 548-557
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Tidskriftsartikel (refereegranskat)abstract
- The concentrations of sulfur and several more elements were measured in a network of six sites in southern Sweden. High time resolution samples were taken using a continuous filter sampler and analysed by particle induced X-ray emission (PIXE). Simultaneous increases in the sulfur concentrations were seen along the network due to the inflow of polluted air masses. High sulfur concentrations generally occurred during south-westerly to easterly air flow. Some of the episodes, distinguished by their shorter duration and their elevated vanadium and nickel concentrations, are suggested to be of local origin.
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