Dynamic proton disorder and the II–I structural phase transition in (NH4)3H(SO4)2

Sohn, Y.J.; Loose, A.; Merz, M.; Sparta, K.; Klapper, H.; Heger, G.

doi:10.1107/S0108768108041876

Dynamic proton disorder and the II-I structural phase transition in (NH₄)₃H(SO₄)₂

Y. J. Sohn, A. Loose, M. Merz, K. Sparta, H. Klapper and G. Heger

X-ray powder diffraction, differential scanning calorimetry (DSC)/thermogravimetry (TG) and single-crystal neutron diffraction methods were used to investigate triammonium hydrogen disulfate (NH₄)₃H(SO₄)₂ (TAHS) in the temperature range between 293 and 493 K. The temperature-dependent X-ray powder diffraction measurements show a clear hysteresis of the I $\leftrightarrow$ II phase transition of TAHS with transition temperatures of T_up = 412.9 (1) K on heating and of T_down = 402.6 (1) K on cooling. From the existence of hysteresis and from the jump-like changes of the lattice parameters, the I $\leftrightarrow$ II phase transition of TAHS is considered to be first order. With DSC/TG measurements we confirmed that there is only one phase transition between 293 and 493 K. Through careful investigation on single crystals of TAHS using neutron diffraction, the correct space group (C2/c) of room-temperature TAHS-II phase was confirmed. Crystal structure analysis by single-crystal neutron diffraction showed a strongly elongated displacement ellipsoid of the proton which lies in the middle of the (SO₄)H(SO₄) dimer with $\bar 1$ local symmetry. The protons of the NH₄ groups also show strongly enlarged anisotropic mean-square displacements. These findings are interpreted in terms of a characteristic proton disorder in the TAHS-II phase.

Keywords: proton disorder; phase transition; powder diffraction.

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Supporting information

	Crystallographic Information File (CIF) https://doi.org/10.1107/S0108768108041876/gw5001sup1.cif Contains datablocks global, nonsplit, split
	Structure factor file (CIF format) https://doi.org/10.1107/S0108768108041876/gw5001nonsplitsup2.hkl Contains datablock nonsplit
	Structure factor file (CIF format) https://doi.org/10.1107/S0108768108041876/gw5001splitsup3.hkl Contains datablock split

Computing details top

For both compounds, data collection: DIF4N (modified Linux version of DIF4; Stoe & Cie, 1991); cell refinement: DIF4N; data reduction: PRON (Scherf, 1998); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: Atoms 5.1; software used to prepare material for publication: ???.

Figures top

(nonsplit) top

Crystal data top

HO₈S₂·3(H₄N)	F(000) = 126
M_r = 247.25	D_x = 1.825 Mg m⁻³ D_m = 1.825 Mg m⁻³ D_m measured by not measured
Monoclinic, C2/c	Melting point: 0 K
Hall symbol: -C 2yc	Neutron radiation, λ = 0.87238 Å
a = 15.429 (8) Å	Cell parameters from 13 reflections
b = 5.861 (3) Å	θ = 17.3–21.6°
c = 10.167 (5) Å	µ = 0.22 mm⁻¹
β = 101.83 (5)°	T = 293 K
V = 899.9 (8) Å³	Cuboid, white
Z = 4	3 × 3 × 3 × 0 (radius) mm

Data collection top

Four circle diffractometer	θ_max = 37.5°, θ_min = 3.3°
ω scans	h = −19→20
1169 measured reflections	k = −1→8
1143 independent reflections	l = −14→11
770 reflections with I > 2σ(I)	2 standard reflections every 600 min
R_int = 0.039	intensity decay: none

Refinement top

Refinement on F²	0 restraints
Least-squares matrix: full	0 constraints
R[F² > 2σ(F²)] = 0.094	All H-atom parameters refined
wR(F²) = 0.144	w = 1/[σ²(F_o²) + (0.P)² + 7.P] where P = (F_o² + 2F_c²)/3
S = 1.97	(Δ/σ)_max < 0.001
1143 reflections	Δρ_max = 1.07 e Å⁻³
120 parameters	Δρ_min = −1.24 e Å⁻³

Crystal data top

HO₈S₂·3(H₄N)	V = 899.9 (8) Å³
M_r = 247.25	Z = 4
Monoclinic, C2/c	Neutron radiation, λ = 0.87238 Å
a = 15.429 (8) Å	µ = 0.22 mm⁻¹
b = 5.861 (3) Å	T = 293 K
c = 10.167 (5) Å	3 × 3 × 3 × 0 (radius) mm
β = 101.83 (5)°

Data collection top

Four circle diffractometer	R_int = 0.039
1169 measured reflections	2 standard reflections every 600 min
1143 independent reflections	intensity decay: none
770 reflections with I > 2σ(I)

Refinement top

R[F² > 2σ(F²)] = 0.094	0 restraints
wR(F²) = 0.144	All H-atom parameters refined
S = 1.97	Δρ_max = 1.07 e Å⁻³
1143 reflections	Δρ_min = −1.24 e Å⁻³
120 parameters

Special details top

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

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
S	0.1150 (3)	0.2175 (10)	0.4630 (6)	0.0237 (10)
N1	0.5	0.2298 (5)	0.25	0.0296 (6)
N2	0.19904 (14)	0.2766 (4)	0.1531 (2)	0.0343 (5)
O1	0.01474 (18)	0.1836 (6)	0.4428 (4)	0.0386 (8)
O2	0.1504 (2)	0.2223 (7)	0.6049 (3)	0.0393 (8)
O3	0.1286 (2)	0.4326 (6)	0.3982 (4)	0.0416 (8)
O4	0.1489 (2)	0.0278 (6)	0.3979 (4)	0.0427 (9)
H1	0	0	0	0.079 (5)
H2	0.4648 (7)	0.131 (2)	0.1834 (11)	0.105 (4)
H3	0.4569 (8)	0.310 (3)	0.2747 (19)	0.171 (8)
H4	0.2601 (6)	0.310 (2)	0.1698 (14)	0.117 (5)
H5	0.1695 (10)	0.387 (3)	0.0978 (16)	0.142 (6)
H6	0.1900 (7)	0.1303 (17)	0.1146 (12)	0.100 (4)
H7	0.1772 (8)	0.283 (3)	0.2313 (10)	0.127 (5)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
S	0.022 (2)	0.025 (2)	0.024 (3)	0.0034 (19)	0.004 (2)	−0.002 (2)
N1	0.0288 (11)	0.0327 (14)	0.0260 (15)	0	0.0025 (12)	0
N2	0.0388 (11)	0.0303 (10)	0.0332 (12)	−0.0074 (9)	0.0057 (9)	−0.0008 (10)
O1	0.0182 (11)	0.0463 (19)	0.050 (2)	0.0017 (12)	0.0032 (12)	−0.0020 (16)
O2	0.0345 (13)	0.057 (2)	0.0240 (14)	−0.0075 (14)	0.0008 (13)	0.0002 (15)
O3	0.0415 (16)	0.0324 (15)	0.049 (2)	0.0023 (13)	0.0048 (14)	0.0176 (15)
O4	0.0364 (14)	0.0354 (16)	0.060 (2)	−0.0002 (13)	0.0184 (16)	−0.0181 (15)
H1	0.026 (3)	0.143 (13)	0.064 (7)	−0.002 (5)	0.001 (4)	0.059 (8)
H2	0.087 (6)	0.128 (9)	0.085 (7)	0.002 (6)	−0.015 (5)	−0.043 (7)
H3	0.089 (7)	0.188 (15)	0.222 (17)	0.064 (9)	0.002 (9)	−0.105 (14)
H4	0.058 (5)	0.117 (9)	0.172 (11)	−0.022 (5)	0.014 (6)	−0.079 (9)
H5	0.135 (10)	0.136 (11)	0.157 (13)	0.055 (9)	0.035 (9)	0.089 (11)
H6	0.094 (6)	0.067 (5)	0.130 (10)	−0.021 (5)	0.001 (6)	−0.054 (6)
H7	0.130 (9)	0.195 (15)	0.069 (6)	−0.037 (10)	0.050 (6)	−0.008 (8)

Geometric parameters (Å, º) top

S—O2	1.434 (7)	N1—H3	0.891 (12)
S—O4	1.446 (6)	N2—H4	0.943 (9)
S—O3	1.458 (6)	N2—H5	0.918 (13)
S—O1	1.531 (5)	N2—H6	0.941 (9)
N1—H2	0.969 (11)	N2—H7	0.925 (10)

O2—S—O4	112.1 (4)	H4—N2—H5	108.3 (14)
O2—S—O3	112.1 (4)	H4—N2—H6	108.9 (9)
O4—S—O3	111.0 (4)	H5—N2—H6	112.1 (13)
O2—S—O1	107.7 (4)	H4—N2—H7	111.3 (11)
O4—S—O1	106.9 (4)	H5—N2—H7	106.0 (15)
O3—S—O1	106.7 (4)	H6—N2—H7	110.2 (14)
H2—N1—H3	99.7 (10)

(split) top

Crystal data top

HO₈S₂·3(H₄N)	F(000) = 126
M_r = 247.25	D_x = 1.825 Mg m⁻³ D_m = 1.825 Mg m⁻³ D_m measured by not measured
Monoclinic, C2/c	Melting point: 0 K
Hall symbol: -C 2yc	Neutron radiation, λ = 0.87238 Å
a = 15.429 (8) Å	Cell parameters from 13 reflections
b = 5.861 (3) Å	θ = 17.3–21.6°
c = 10.167 (5) Å	µ = 0.22 mm⁻¹
β = 101.83 (5)°	T = 293 K
V = 899.9 (8) Å³	Cuboid, white
Z = 4	3 × 3 × 3 × 0 (radius) mm

Data collection top

Four circle diffractometer	θ_max = 37.5°, θ_min = 3.3°
ω scans	h = −19→20
1169 measured reflections	k = −1→8
1143 independent reflections	l = −14→11
770 reflections with I > 2σ(I)	2 standard reflections every 600 min
R_int = 0.039	intensity decay: none

Refinement top

Refinement on F²	0 restraints
Least-squares matrix: full	0 constraints
R[F² > 2σ(F²)] = 0.094	All H-atom parameters refined
wR(F²) = 0.144	w = 1/[σ²(F_o²) + (0.P)² + 7.P] where P = (F_o² + 2F_c²)/3
S = 1.98	(Δ/σ)_max < 0.001
1143 reflections	Δρ_max = 1.11 e Å⁻³
118 parameters	Δρ_min = −1.24 e Å⁻³

Crystal data top

HO₈S₂·3(H₄N)	V = 899.9 (8) Å³
M_r = 247.25	Z = 4
Monoclinic, C2/c	Neutron radiation, λ = 0.87238 Å
a = 15.429 (8) Å	µ = 0.22 mm⁻¹
b = 5.861 (3) Å	T = 293 K
c = 10.167 (5) Å	3 × 3 × 3 × 0 (radius) mm
β = 101.83 (5)°

Data collection top

Four circle diffractometer	R_int = 0.039
1169 measured reflections	2 standard reflections every 600 min
1143 independent reflections	intensity decay: none
770 reflections with I > 2σ(I)

Refinement top

R[F² > 2σ(F²)] = 0.094	0 restraints
wR(F²) = 0.144	All H-atom parameters refined
S = 1.98	Δρ_max = 1.11 e Å⁻³
1143 reflections	Δρ_min = −1.24 e Å⁻³
118 parameters

Special details top

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq	Occ. (<1)
S	0.1150 (3)	0.2176 (10)	0.4629 (6)	0.0232 (10)
N1	0.5	0.2298 (5)	0.25	0.0292 (6)
N2	0.19905 (14)	0.2765 (4)	0.1531 (2)	0.0339 (5)
O1	0.01501 (17)	0.1849 (6)	0.4426 (4)	0.0391 (8)
O2	0.1504 (2)	0.2223 (7)	0.6049 (3)	0.0390 (8)
O3	0.1286 (2)	0.4326 (6)	0.3981 (4)	0.0412 (8)
O4	0.1490 (2)	0.0278 (6)	0.3979 (4)	0.0422 (9)
H1	−0.0006 (8)	0.0424 (16)	0.0134 (12)	0.035 (2)*	0.5
H2	0.4648 (7)	0.130 (2)	0.1834 (11)	0.104 (4)
H3	0.4567 (8)	0.309 (3)	0.2749 (19)	0.171 (8)
H4	0.2602 (6)	0.310 (2)	0.1698 (14)	0.116 (4)
H5	0.1694 (10)	0.388 (3)	0.0978 (16)	0.141 (6)
H6	0.1900 (7)	0.1304 (16)	0.1145 (12)	0.100 (4)
H7	0.1771 (8)	0.283 (3)	0.2314 (10)	0.126 (5)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
S	0.021 (2)	0.025 (2)	0.023 (3)	0.0036 (19)	0.004 (2)	−0.001 (2)
N1	0.0285 (11)	0.0322 (14)	0.0256 (15)	0	0.0022 (12)	0
N2	0.0384 (11)	0.0300 (10)	0.0327 (11)	−0.0074 (9)	0.0055 (9)	−0.0007 (10)
O1	0.0184 (10)	0.0462 (19)	0.052 (2)	0.0003 (12)	0.0044 (12)	−0.0007 (15)
O2	0.0342 (13)	0.057 (2)	0.0237 (14)	−0.0075 (14)	0.0007 (13)	0.0001 (15)
O3	0.0413 (16)	0.0319 (15)	0.048 (2)	0.0022 (13)	0.0048 (14)	0.0177 (15)
O4	0.0362 (14)	0.0346 (16)	0.059 (2)	0.0001 (13)	0.0184 (16)	−0.0180 (15)
H2	0.085 (6)	0.127 (9)	0.085 (7)	0.000 (6)	−0.015 (5)	−0.044 (7)
H3	0.089 (7)	0.186 (15)	0.224 (17)	0.063 (9)	0.003 (9)	−0.104 (14)
H4	0.057 (4)	0.117 (9)	0.171 (11)	−0.022 (5)	0.014 (6)	−0.079 (8)
H5	0.134 (10)	0.135 (11)	0.157 (13)	0.055 (9)	0.034 (9)	0.089 (11)
H6	0.093 (6)	0.067 (5)	0.130 (10)	−0.022 (5)	0.001 (6)	−0.054 (6)
H7	0.130 (9)	0.193 (15)	0.068 (6)	−0.035 (10)	0.051 (6)	−0.007 (8)

Geometric parameters (Å, º) top

S—O2	1.434 (7)	N1—H3	0.893 (12)
S—O4	1.446 (6)	N2—H4	0.944 (9)
S—O3	1.457 (6)	N2—H5	0.919 (13)
S—O1	1.526 (5)	N2—H6	0.940 (9)
N1—H2	0.972 (11)	N2—H7	0.928 (10)

O2—S—O4	112.1 (4)	H4—N2—H5	108.4 (14)
O2—S—O3	112.2 (4)	H4—N2—H6	108.8 (9)
O4—S—O3	111.1 (4)	H5—N2—H6	112.2 (13)
O2—S—O1	107.7 (4)	H4—N2—H7	111.3 (11)
O4—S—O1	107.0 (4)	H5—N2—H7	105.9 (15)
O3—S—O1	106.4 (4)	H6—N2—H7	110.3 (13)
H2—N1—H3	99.7 (10)

Experimental details

	(nonsplit)	(split)
Crystal data
Chemical formula	HO₈S₂·3(H₄N)	HO₈S₂·3(H₄N)
M_r	247.25	247.25
Crystal system, space group	Monoclinic, C2/c	Monoclinic, C2/c
Temperature (K)	293	293
a, b, c (Å)	15.429 (8), 5.861 (3), 10.167 (5)	15.429 (8), 5.861 (3), 10.167 (5)
β (°)	101.83 (5)	101.83 (5)
V (Å³)	899.9 (8)	899.9 (8)
Z	4	4
Radiation type	Neutron, λ = 0.87238 Å	Neutron, λ = 0.87238 Å
µ (mm⁻¹)	0.22	0.22
Crystal size (mm)	3 × 3 × 3 × 0 (radius)	3 × 3 × 3 × 0 (radius)

Data collection
Diffractometer	Four circle diffractometer	Four circle diffractometer
Absorption correction	–	–
No. of measured, independent and observed [I > 2σ(I)] reflections	1169, 1143, 770	1169, 1143, 770
R_int	0.039	0.039
(sin θ/λ)_max (Å⁻¹)	0.697	0.697

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.094, 0.144, 1.97	0.094, 0.144, 1.98
No. of reflections	1143	1143
No. of parameters	120	118
H-atom treatment	All H-atom parameters refined	All H-atom parameters refined
Δρ_max, Δρ_min (e Å⁻³)	1.07, −1.24	1.11, −1.24

Computer programs: DIF4N (modified Linux version of DIF4; Stoe & Cie, 1991), DIF4N, PRON (Scherf, 1998), SHELXL97 (Sheldrick, 1997), Atoms 5.1, ???.

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Dynamic proton disorder and the II-I structural phase transition in (NH4)3H(SO4)2

Supporting information

Dynamic proton disorder and the II-I structural phase transition in (NH₄)₃H(SO₄)₂