ISSN:
1600-5740
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
Notes:
The crystal structures of NaK1−x(NH4)x(+)-C4H4O6.4H2O (RS1−xARSx, x = 0.90, 0.94 and 1.00) have been determined in the paraelectric phase (T = 294 K). The crystal data are: for ARS, orthorhombic, P21212, R = 0.038, wR = 0.032, no. of reflections = 3373, a = 12.206 (7), b = 14.451 (6), c = 6.250 (4) Å, V = 1102 (1) Å3, Z = 4, Dx = 1.573 g cm−3, λ(MoKα) = 0.70926 Å, F(000) = 552.00; for RS0.06ARS0.94, orthorhombic, P21212, R = 0.040, wR = 0.030, no. of reflections = 2446, a = 12.172 (4), b = 14.421 (4), c = 6.239 (2) Å, V = 1095.2 (6) Å3, Z = 4, Dx = 1.592 g cm−3, λ(Mo Kα1) = 0.70926 Å, F(000) = 553.92; for RS0.10ARS0.90, orthorhombic, P21212, R = 0.036, wR = 0.027, no. of reflections = 1898, a = 12.165 (9), b = 14.420 (7), c = 6.239 (4) Å, V = 1094 (1) Z = 4, Dx = 1.598 g cm−3, λ(Mo Kα1) = 0.70926 Å, F(000) = 555.20. In the crystals there are two crystallographically nonequivalent cation sites occupied by K/NH4 ions. The accommodation ratios of sites (1) [(2a) by the Wyckoff notation] and (2) [(2b)] are 0.94 (1) and 0.92 (1), respectively, in RS0.06ARS0.94, and 0.90 (1) and 0.93 (1), respectively, in RS0.10ARS0.90. As x increases, the location of site (2) displaces towards the origin. The hydrogen bonds around sites (1) and (2) are classified into two types: one is that the distances become longer as x increases, due to the difference in the ionic radii of K and NH4 ions, while the other is that the distances are equal. Comparing the crystal structure of ARS to that of RS, the following differences occur: the position of site (2), the interatomic distances between cations of sites (1) and (2) and O atoms, the form of the tartrate molecule and the position of some water molecules. These differences seem to be mainly caused by the replacement of NH4 ions by K.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S0108768195010822
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