Le dichlorure et le dibromure de calcium hexahydratés

Leclaire, A.; Borel, M.M.

doi:10.1107/s0567740877009881

Cited by 31 publications

(36 citation statements)

References 3 publications

(3 reference statements)

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“…Lattice parameters from least-squares refinement based on X-ray diffractometer Bragg angles for 12 high-angle reflections (20= 120 to 130°); Cu Kcq radiation, 2 = 1.54051 A. Results agree with reported values (Herrmann, 1930(Herrmann, , 1931Jensen, 1940;Leclaire & Borel, 1977;English & Nassimbeni, 1984).…”

supporting

confidence: 82%

“…Table 2 lists the fractional coordinates and equivalent isotropic thermal parameters. The oxygen positions for CaCIz.6H20 are in good agreement with the X-ray results of Leclaire & Borel (1977), and the hydrogen positions are roughly the same as those which they obtained from electrostatic calculations (Baur, 1965). These authors correctly deduced that there was a typographical error, later corrected, in our original report (Agron & Busing, 1969).…”

supporting

confidence: 78%

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Calcium and strontium dichloride hexahydrates by neutron diffraction

Agron¹,

Busing²

1986

Acta Crystallogr C Cryst Struct Commun

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Abstract. CAC12.6H20 and SrC12.6H20, isotypic, trigonal, P321, Z= 1, unit cells from X-ray CuKa 1, 2 x= 1.54051, 2N= 1"077]~, room temperature. CaCI2.6H20, M r = 219.08, a = 7.8759 (2), c = 3.9545 (2),/~, V= 212.43 (6),/k 3, D m= 1.71, Dx= 1.7126 gcm -3, g = 2.566 cm -~, F(000) = 14.00 fm, R(F) --0.0287 for 304 unique reflections. SrCI~.6H20, M r=266.62, a=7.9596(3), c=4.1243(2) A, V= 226.29 A 3, D m = 1.93, D x = 1.9565 g cm -3, g = 2.430 cm -1, F(000) = 16.12 fm, R(F) = 0.0356 for 325 unique reflections. Nine water molecules are coordinated to each metal ion. Three of these adjoin only one cation and six are shared between two such ions. These water molecules are hydrogen-bonded to the CI-ions so that each anion is surrounded by six H atoms in a distorted octahedral arrangement.Introduction. These single-crystal neutron diffraction studies are part of a program to locate the H atoms precisely and to investigate the role of water in simple salt hydrates.

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supporting

confidence: 82%

supporting

confidence: 78%

Calcium and strontium dichloride hexahydrates by neutron diffraction

Agron¹,

Busing²

1986

Acta Crystallogr C Cryst Struct Commun

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“…11 Moreover, a number of reasonably well-determined crystal structures can be selected which contain discrete hydrated calcium(II) ions only surrounded by water molecules O w , for hydration numbers from 6 to 9. All these structures display a more or less wide distribution of the Ca-O w distances, but the arithmetic mean values were found to vary little for the same hydration number: Ca-6O w 2.31-2.33 Å, [54][55][56] Ca-7O w 2.40- 65,66 Another correlation (Table 5) can be obtained from the effective ionic radii given by Shannon,67 in combination with the estimated radius of the water molecule, 1.34 Å, derived from structure studies of the cesium alum salts. 68 Thus, the mean Ca-O distance obtained from both the LAXS and EXAFS data, ca.…”

Section: Comparison With Hydrated Calcium Ions In Crystal Structuresmentioning

confidence: 90%

Hydration of the Calcium Ion. An EXAFS, Large-Angle X-ray Scattering, and Molecular Dynamics Simulation Study

et al. 2000

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The structure of the hydrated calcium(II) ion in aqueous solution has been studied by means of extended X-ray absorption fine structure spectroscopy (EXAFS), large-angle X-ray scattering (LAXS), and molecular dynamics (MD) methods. The EXAFS data displayed a broad and asymmetric distribution of the Ca-O bond distances with the centroid at 2.46(2) A. LAXS studies on four aqueous calcium halide solutions (1.5-2 mol dm(-)(3)) gave a mean Ca-O bond distance of 2.46(1) A. This is consistent with a hydration number of 8 determined from correlations between mean distances and coordination numbers from crystal structures. The LAXS studies showed a second coordination sphere with a mean Ca.O(II) distance of 4.58(5) A, and for the hydrated halide ions the distances Cl.O 3.25(1) A, Br.O 3.36(1) A, and I.O 3.61(1) A were obtained. Molecular dynamics simulations of CaCl(2)(aq) were performed using three different Ca(2+)-OH(2) pair potentials. The potential from the GROMOS program gave results in agreement with experiments, i.e., a coordination number of 8 and an average Ca-O distance of 2.46 A, and was used for further comparisons. Theoretical EXAFS oscillations were computed for individual MD snapshots and showed very large variations, though the simulated average spectrum from 2000 snapshots gave satisfactory agreement with the experimental EXAFS spectra. The effect of thermal motions of the coordinated atoms is inherent in the MD simulation method. Thermal disorder parameters evaluated from simulated spatial atom distribution functions of the oxygen atoms coordinated to the calcium ion were in close agreement with those from the current LAXS and EXAFS analyses. The combined results are consistent with a root-mean-square displacement from the mean Ca-O distance of 0.09(2) A in aqueous solution at 300 K.

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“…SrBr2.6H20 is isostructural with CaBr2.6H20 (Leclaire & Borel, 1977). The strontium and calcium dichloride hexahydrates are also isostructural.…”

Section: Commentmentioning

confidence: 78%