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The structure of the mixed crystal [K1−x(NH4)x]3H(SO4)2 as obtained from single-crystal neutron diffraction is compared with the previously reported room-temperature neutron structure of crystalline K3H(SO4)2. The two structures are very similar, as indicated by the high value of their isostructurality index (94.8%). It was found that the replacement of even a small amount (3%) of K+ with NH4+ has a significant influence on the short strong hydrogen bond connecting the two SO42− ions. Earlier optical measurements had revealed that the kinetics of the superionic transition in the solid solution [K1−x(NH4)x]3H(SO4)2 are much faster than in K3H(SO4)2; this reported difference in the kinetics of the superionic phase transition in this class of crystal is explained on the basis of the difference in strength of the hydrogen-bond interactions in the two structures.

Supporting information


Crystallographic Information File (CIF)
Contains datablock I


Structure factor file (CIF format)
Contains datablock I

CCDC reference: 1555199

Computing details top

Program(s) used to refine structure: SHELXL97 (Sheldrick, 1997).

(I) top
Crystal data top
HK2.91N0.09O8S2Z = 2
Mr = 616.34F(000) = 240
Monoclinic, C2/cDx = 2.574 Mg m3
a = 14.692 (2) ÅNeutron radiation, λ = 0.99600 Å
b = 5.681 (1) ÅCell parameters from 50 reflections
c = 9.776 (1) Åθ = 4.0–44.2°
β = 102.99 (1)°T = 293 K
V = 795.08 (19) Å3, transparent
Data collection top
Radiation source: Dhruva reactorRint = 0.040
Copper monochromatorθmax = 44.2°, θmin = 4.0°
1211 measured reflectionsh = 2012
1094 independent reflectionsk = 77
606 reflections with I > 2σ(I)l = 813
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.139Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.387H atoms treated by a mixture of independent and constrained refinement
S = 1.10 w = 1/[σ2(Fo2) + (0.0853P)2 + 0.8246P]
where P = (Fo2 + 2Fc2)/3
1094 reflections(Δ/σ)max < 0.001
65 parametersΔρmax = 0.23 e Å3
0 restraintsΔρmin = 0.23 e Å3
Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > 2sigma(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/UeqOcc. (<1)
K11.00000.7536 (18)0.75000.0279 (17)0.97
N11.00000.7536 (18)0.75000.0279 (17)0.03
K20.3045 (5)0.7392 (13)0.3503 (7)0.0323 (14)0.97
N20.3045 (5)0.7392 (13)0.3503 (7)0.0323 (14)0.03
S0.3843 (5)0.7653 (15)0.0420 (8)0.0221 (15)
O10.3478 (4)0.9716 (8)0.1016 (5)0.0332 (11)
O20.4898 (4)0.8071 (14)0.0614 (10)0.057 (2)
O30.3510 (4)0.7563 (10)0.8898 (5)0.0349 (11)
O40.3644 (4)0.5497 (8)0.1075 (5)0.0375 (13)
H10.50000.00000.00000.110 (15)
Atomic displacement parameters (Å2) top
K10.035 (5)0.027 (4)0.021 (3)0.0000.005 (3)0.000
N10.035 (5)0.027 (4)0.021 (3)0.0000.005 (3)0.000
K20.043 (4)0.024 (3)0.031 (3)0.0020.011 (3)0.000 (3)
N20.043 (4)0.024 (3)0.031 (3)0.0020.011 (3)0.000 (3)
S0.021 (3)0.022 (3)0.023 (3)0.000 (3)0.006 (2)0.001 (3)
O10.041 (3)0.024 (2)0.035 (2)0.0019 (18)0.0093 (18)0.0071 (17)
O20.017 (2)0.068 (5)0.083 (6)0.000 (3)0.005 (3)0.030 (4)
O30.049 (3)0.034 (2)0.0251 (18)0.005 (2)0.0149 (17)0.002 (2)
O40.057 (3)0.025 (2)0.029 (2)0.006 (2)0.005 (2)0.0056 (18)
H10.021 (6)0.25 (5)0.055 (10)0.018 (15)0.002 (6)0.07 (2)
Geometric parameters (Å, º) top
S—O41.442 (10)S—O21.537 (10)
S—O3i1.459 (9)O3—Sii1.459 (9)
S—O11.464 (9)
O4—S—O3i111.6 (6)O4—S—O2112.1 (7)
O4—S—O1112.0 (6)O3i—S—O2103.2 (6)
O3i—S—O1111.4 (6)O1—S—O2106.1 (6)
Symmetry codes: (i) x, y, z1; (ii) x, y, z+1.

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