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
CCDC reference: 1555199
Program(s) used to refine structure: SHELXL97 (Sheldrick, 1997).
Crystal data top
HK2.91N0.09O8S2 | Z = 2 |
Mr = 616.34 | F(000) = 240 |
Monoclinic, C2/c | Dx = 2.574 Mg m−3 |
a = 14.692 (2) Å | Neutron radiation, λ = 0.99600 Å |
b = 5.681 (1) Å | Cell parameters from 50 reflections |
c = 9.776 (1) Å | θ = 4.0–44.2° |
β = 102.99 (1)° | T = 293 K |
V = 795.08 (19) Å3 | , transparent |
Data collection top
Radiation source: Dhruva reactor | Rint = 0.040 |
Copper monochromator | θmax = 44.2°, θmin = 4.0° |
1211 measured reflections | h = −20→12 |
1094 independent reflections | k = −7→7 |
606 reflections with I > 2σ(I) | l = −8→13 |
Refinement top
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.139 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.387 | H 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 parameters | Δρmax = 0.23 e Å−3 |
0 restraints | Δρmin = −0.23 e Å−3 |
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 | x | y | z | Uiso*/Ueq | Occ. (<1) |
K1 | 1.0000 | −0.7536 (18) | 0.7500 | 0.0279 (17) | 0.97 |
N1 | 1.0000 | −0.7536 (18) | 0.7500 | 0.0279 (17) | 0.03 |
K2 | 0.3045 (5) | 0.7392 (13) | 0.3503 (7) | 0.0323 (14) | 0.97 |
N2 | 0.3045 (5) | 0.7392 (13) | 0.3503 (7) | 0.0323 (14) | 0.03 |
S | 0.3843 (5) | 0.7653 (15) | 0.0420 (8) | 0.0221 (15) | |
O1 | 0.3478 (4) | 0.9716 (8) | 0.1016 (5) | 0.0332 (11) | |
O2 | 0.4898 (4) | 0.8071 (14) | 0.0614 (10) | 0.057 (2) | |
O3 | 0.3510 (4) | 0.7563 (10) | 0.8898 (5) | 0.0349 (11) | |
O4 | 0.3644 (4) | 0.5497 (8) | 0.1075 (5) | 0.0375 (13) | |
H1 | 0.5000 | 0.0000 | 0.0000 | 0.110 (15) | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
K1 | 0.035 (5) | 0.027 (4) | 0.021 (3) | 0.000 | 0.005 (3) | 0.000 |
N1 | 0.035 (5) | 0.027 (4) | 0.021 (3) | 0.000 | 0.005 (3) | 0.000 |
K2 | 0.043 (4) | 0.024 (3) | 0.031 (3) | −0.002 | 0.011 (3) | 0.000 (3) |
N2 | 0.043 (4) | 0.024 (3) | 0.031 (3) | −0.002 | 0.011 (3) | 0.000 (3) |
S | 0.021 (3) | 0.022 (3) | 0.023 (3) | 0.000 (3) | 0.006 (2) | −0.001 (3) |
O1 | 0.041 (3) | 0.024 (2) | 0.035 (2) | −0.0019 (18) | 0.0093 (18) | −0.0071 (17) |
O2 | 0.017 (2) | 0.068 (5) | 0.083 (6) | 0.000 (3) | 0.005 (3) | −0.030 (4) |
O3 | 0.049 (3) | 0.034 (2) | 0.0251 (18) | −0.005 (2) | 0.0149 (17) | −0.002 (2) |
O4 | 0.057 (3) | 0.025 (2) | 0.029 (2) | 0.006 (2) | 0.005 (2) | 0.0056 (18) |
H1 | 0.021 (6) | 0.25 (5) | 0.055 (10) | 0.018 (15) | −0.002 (6) | −0.07 (2) |
Geometric parameters (Å, º) top
S—O4 | 1.442 (10) | S—O2 | 1.537 (10) |
S—O3i | 1.459 (9) | O3—Sii | 1.459 (9) |
S—O1 | 1.464 (9) | | |
| | | |
O4—S—O3i | 111.6 (6) | O4—S—O2 | 112.1 (7) |
O4—S—O1 | 112.0 (6) | O3i—S—O2 | 103.2 (6) |
O3i—S—O1 | 111.4 (6) | O1—S—O2 | 106.1 (6) |
Symmetry codes: (i) x, y, z−1; (ii) x, y, z+1. |