Oriented single crystals of the high-temperature phase of KNO_{3} (phase III), a ferroelectric compound that may also occur as an atmospheric aerosol particle, were grown at room temperature and pressure by atomizing a solution of KNO_{3} in water and allowing droplets to dry on a glass substrate. The crystals are up to 1 mm across and are stable unless mechanically disturbed. There is no evidence of the spontaneous transformation of phase III to the room-temperature stable phase (phase II), even after several months. Single-crystal structure determinations of phase III were obtained at 295 and 123 K. The unit cell regained its room-temperature dimensions after warming from 123 K. The phase-III KNO_{3} structure can be viewed as the stacking parallel to the c axis of alternating K atoms and planar NO_{3} groups. The NO_{3} groups connect the planes of K atoms, where each O is fourfold coordinated to one N and three K. Each K atom has nine O nearest neighbors, with three bonds at 2.813 and six at 2.9092 Å. The interatomic K-N-K distance alternates from 5.051 to 3.941 along the c axis. The N-O distances increase from 1.245 (2) Å at 295 K to 1.2533 (15) Å at 123 K. The nitrate group has a slight non-planarity, with the N atoms 0.011 Å above the O plane and directed toward the more distant K of the K-N-K chain.
Supporting information
For both compounds, data collection: SMART V5.632; cell refinement: SAINT V6.45A; data reduction: SAINT V6.45A; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL Version 6.14 (Sheldrick, 2003b); software used to prepare material for publication: SHELXTL Version 6.14 (Sheldrick, 2003b).
Crystal data top
KNO_{3} | D_{x} = 2.162 Mg m^{−}^{3} |
M_{r} = 101.11 | Mo Kα radiation, λ = 0.71073 Å |
Hexagonal, R3m | Cell parameters from 715 reflections |
Hall symbol: R 3 -2" | θ = 4.9–27.4° |
a = 5.4698 (8) Å | µ = 1.50 mm^{−}^{1} |
c = 8.992 (3) Å | T = 298 K |
V = 232.99 (8) Å^{3} | Plate, colorless |
Z = 3 | 0.11 × 0.08 × 0.02 mm |
F(000) = 150 | |
Data collection top
Bruker SMART APEX diffractometer | 157 independent reflections |
Radiation source: fine-focus sealed tube | 157 reflections with I > 2σ(I) |
Graphite monochromator | R_{int} = 0.024 |
ω scan | θ_{max} = 27.4°, θ_{min} = 4.9° |
Absorption correction: multi-scan SADABS Version 2.10 (Sheldrick, 2003a) | h = −7→7 |
T_{min} = 0.858, T_{max} = 0.966 | k = −7→7 |
764 measured reflections | l = −11→11 |
Refinement top
Refinement on F^{2} | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | w = 1/[σ^{2}(F_{o}^{2}) + (0.0348P)^{2} + 0.0102P] where P = (F_{o}^{2} + 2F_{c}^{2})/3 |
R[F^{2} > 2σ(F^{2})] = 0.022 | (Δ/σ)_{max} < 0.001 |
wR(F^{2}) = 0.054 | Δρ_{max} = 0.13 e Å^{−}^{3} |
S = 1.23 | Δρ_{min} = −0.16 e Å^{−}^{3} |
157 reflections | Extinction correction: SHELXL, Fc^{*}=kFc[1+0.001xFc^{2}λ^{3}/sin(2θ)]^{-1/4} |
13 parameters | Extinction coefficient: 0.157 (16) |
0 restraints | Absolute structure: Flack H D (1983), Acta Cryst. A39, 876-881 |
Primary atom site location: structure-invariant direct methods | Absolute structure parameter: −0.03 (8) |
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. |
Refinement. Refinement of F^{2} against ALL reflections. The weighted R-factor
wR and goodness of fit S are based on F^{2}, conventional
R-factors R are based on F, with F set to zero for
negative F^{2}. The threshold expression of F^{2} >
σ(F^{2}) is used only for calculating R-factors(gt) etc.
and is not relevant to the choice of reflections for refinement.
R-factors based on F^{2} 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 (Å^{2}) top | x | y | z | U_{iso}*/U_{eq} | |
K1 | 0.0000 | 0.0000 | 0.5000 | 0.0357 (4) | |
N1 | 0.6667 | 0.3333 | 0.3950 (4) | 0.0312 (8) | |
O1 | 0.5352 (2) | 0.0705 (4) | 0.3961 (2) | 0.0467 (6) | |
Atomic displacement parameters (Å^{2}) top | U^{11} | U^{22} | U^{33} | U^{12} | U^{13} | U^{23} |
K1 | 0.0298 (4) | 0.0298 (4) | 0.0475 (5) | 0.01488 (19) | 0.000 | 0.000 |
N1 | 0.0296 (12) | 0.0296 (12) | 0.0345 (13) | 0.0148 (6) | 0.000 | 0.000 |
O1 | 0.0403 (10) | 0.0267 (9) | 0.0685 (13) | 0.0133 (5) | 0.0002 (4) | 0.0003 (8) |
Geometric parameters (Å, º) top
K1—O1^{i} | 2.813 (2) | K1—K1^{v} | 4.3540 (7) |
K1—O1^{ii} | 2.814 (2) | N1—O1^{vi} | 1.245 (2) |
K1—O1^{iii} | 2.9092 (9) | O1—K1^{vii} | 2.9092 (8) |
K1—N1^{iv} | 3.2962 (11) | | |
| | | |
O1^{i}—K1—O1^{ii} | 72.14 (7) | O1^{i}—K1—K1^{v} | 138.713 (16) |
O1^{i}—K1—O1^{iii} | 145.89 (7) | O1^{ii}—K1—K1^{v} | 138.712 (15) |
O1^{ii}—K1—O1^{iii} | 99.06 (4) | O1^{viii}—K1—K1^{v} | 90.67 (5) |
O1^{viii}—K1—O1^{iii} | 73.80 (2) | O1^{iii}—K1—K1^{v} | 39.65 (4) |
O1^{iii}—K1—O1^{ix} | 43.52 (8) | O1^{ix}—K1—K1^{v} | 72.29 (4) |
O1^{iii}—K1—O1 | 140.13 (8) | O1—K1—K1^{v} | 114.27 (4) |
O1^{ix}—K1—O1 | 110.20 (4) | N1^{iv}—K1—K1^{v} | 56.99 (4) |
O1^{iii}—K1—O1^{x} | 69.42 (8) | N1^{iii}—K1—K1^{v} | 57.00 (4) |
O1^{ix}—K1—O1^{x} | 110.21 (4) | O1^{vi}—N1—O1 | 119.993 (6) |
O1^{i}—K1—O1^{xi} | 73.798 (19) | O1^{vi}—N1—O1^{xii} | 119.994 (6) |
O1^{i}—K1—N1^{iv} | 83.37 (5) | O1—N1—O1^{xii} | 119.992 (6) |
O1^{ii}—K1—N1^{iv} | 149.48 (8) | O1^{vi}—N1—K1^{vii} | 162.9 (2) |
O1^{iii}—K1—N1^{iv} | 91.03 (4) | O1—N1—K1^{vii} | 61.22 (5) |
O1^{ix}—K1—N1^{iv} | 129.28 (6) | K1^{vii}—N1—K1^{xiii} | 112.14 (5) |
O1^{x}—K1—N1^{iv} | 22.03 (4) | N1—O1—K1^{xiv} | 132.4 (2) |
O1^{xi}—K1—N1^{iv} | 22.04 (4) | N1—O1—K1 | 96.74 (7) |
O1^{ii}—K1—N1^{iii} | 83.36 (5) | K1^{xiv}—O1—K1 | 99.06 (4) |
N1^{iv}—K1—N1^{iii} | 112.14 (5) | K1—O1—K1^{vii} | 140.13 (8) |
Symmetry codes: (i) −x+y+2/3, −x+1/3, z+1/3; (ii) x−1/3, y+1/3, z+1/3; (iii) x−1, y, z; (iv) x−1, y−1, z; (v) x−2/3, y−1/3, z−1/3; (vi) −x+y+1, −x+1, z; (vii) x+1, y, z; (viii) −y−1/3, x−y−2/3, z+1/3; (ix) −y, x−y, z; (x) −x+y, −x, z; (xi) −y, x−y−1, z; (xii) −y+1, x−y, z; (xiii) x+1, y+1, z; (xiv) x+1/3, y−1/3, z−1/3. |
Crystal data top
KNO_{3} | D_{x} = 2.233 Mg m^{−}^{3} |
M_{r} = 101.11 | Mo Kα radiation, λ = 0.71073 Å |
Hexagonal, R3m | Cell parameters from 750 reflections |
Hall symbol: R 3 -2" | θ = 4.9–27.5° |
a = 5.4325 (2) Å | µ = 1.55 mm^{−}^{1} |
c = 8.8255 (7) Å | T = 123 K |
V = 225.56 (2) Å^{3} | Plate, colorless |
Z = 3 | 0.11 × 0.08 × 0.02 mm |
F(000) = 150 | |
Data collection top
Bruker SMART APEX diffractometer | 155 independent reflections |
Radiation source: fine-focus sealed tube | 155 reflections with I > 2σ(I) |
Graphite monochromator | R_{int} = 0.014 |
ω scan | θ_{max} = 27.5°, θ_{min} = 4.9° |
Absorption correction: multi-scan SADABS Version 2.10 (Sheldrick, 2003a) | h = −7→7 |
T_{min} = 0.854, T_{max} = 0.965 | k = −7→7 |
755 measured reflections | l = −11→11 |
Refinement top
Refinement on F^{2} | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F^{2} > 2σ(F^{2})] = 0.017 | w = 1/[σ^{2}(F_{o}^{2}) + (0.0254P)^{2} + 0.214P] where P = (F_{o}^{2} + 2F_{c}^{2})/3 |
wR(F^{2}) = 0.041 | (Δ/σ)_{max} < 0.001 |
S = 1.14 | Δρ_{max} = 0.18 e Å^{−}^{3} |
155 reflections | Δρ_{min} = −0.19 e Å^{−}^{3} |
12 parameters | Absolute structure: Flack H D (1983), Acta Cryst. A39, 876-881 |
0 restraints | Absolute structure parameter: −0.05 (7) |
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. |
Refinement. Refinement of F^{2} against ALL reflections. The weighted R-factor
wR and goodness of fit S are based on F^{2}, conventional
R-factors R are based on F, with F set to zero for
negative F^{2}. The threshold expression of F^{2} >
σ(F^{2}) is used only for calculating R-factors(gt) etc.
and is not relevant to the choice of reflections for refinement.
R-factors based on F^{2} 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 (Å^{2}) top | x | y | z | U_{iso}*/U_{eq} | |
K1 | 0.0000 | 0.0000 | 0.5000 | 0.0153 (2) | |
N1 | 0.6667 | 0.3333 | 0.3975 (3) | 0.0133 (6) | |
O1 | 0.53347 (16) | 0.0669 (3) | 0.39836 (16) | 0.0185 (4) | |
Atomic displacement parameters (Å^{2}) top | U^{11} | U^{22} | U^{33} | U^{12} | U^{13} | U^{23} |
K1 | 0.0130 (2) | 0.0130 (2) | 0.0200 (3) | 0.00650 (12) | 0.000 | 0.000 |
N1 | 0.0128 (9) | 0.0128 (9) | 0.0142 (11) | 0.0064 (4) | 0.000 | 0.000 |
O1 | 0.0163 (7) | 0.0101 (7) | 0.0271 (8) | 0.0051 (3) | −0.0001 (3) | −0.0003 (5) |
Geometric parameters (Å, º) top
K1—O1^{i} | 2.7799 (14) | K1—K1^{iv} | 4.3002 (2) |
K1—O1^{ii} | 2.8778 (5) | N1—O1^{v} | 1.2533 (15) |
K1—N1^{iii} | 3.2643 (9) | O1—K1^{vi} | 2.7798 (14) |
| | | |
O1^{i}—K1—O1^{vii} | 71.84 (5) | O1^{i}—K1—K1^{iv} | 138.615 (9) |
O1^{i}—K1—O1^{ii} | 98.93 (3) | O1^{vii}—K1—K1^{iv} | 138.614 (9) |
O1^{vii}—K1—O1^{ii} | 145.09 (5) | O1^{viii}—K1—K1^{iv} | 90.52 (3) |
O1^{viii}—K1—O1^{ii} | 73.299 (11) | O1^{ii}—K1—K1^{iv} | 39.69 (3) |
O1^{ii}—K1—O1^{ix} | 44.32 (6) | O1^{ix}—K1—K1^{iv} | 72.96 (3) |
O1^{ii}—K1—O1^{x} | 141.42 (5) | O1^{x}—K1—K1^{iv} | 115.02 (3) |
O1^{ix}—K1—O1^{x} | 110.75 (3) | N1^{iii}—K1—K1^{iv} | 57.32 (3) |
O1^{vii}—K1—O1^{xi} | 98.92 (3) | O1^{v}—N1—O1 | 119.996 (4) |
O1^{viii}—K1—O1^{xi} | 73.298 (11) | O1^{v}—N1—K1^{xii} | 61.18 (4) |
O1^{ii}—K1—O1^{xi} | 69.04 (6) | O1^{x}—N1—K1^{xii} | 163.6 (2) |
O1^{i}—K1—N1^{iii} | 83.01 (4) | K1^{xii}—N1—K1^{xiii} | 112.63 (4) |
O1^{vii}—K1—N1^{iii} | 148.73 (6) | N1—O1—K1^{vi} | 132.30 (16) |
O1^{ii}—K1—N1^{iii} | 22.43 (3) | N1—O1—K1 | 96.39 (6) |
O1^{x}—K1—N1^{iii} | 130.28 (5) | K1^{vi}—O1—K1 | 98.93 (3) |
O1^{xi}—K1—N1^{iii} | 91.08 (3) | K1—O1—K1^{xii} | 141.42 (5) |
N1^{iii}—K1—N1^{xi} | 112.63 (5) | | |
Symmetry codes: (i) −x+y+2/3, −x+1/3, z+1/3; (ii) −x+y, −x, z; (iii) x−1, y−1, z; (iv) x−2/3, y−1/3, z−1/3; (v) −y+1, x−y, z; (vi) x+1/3, y−1/3, z−1/3; (vii) x−1/3, y+1/3, z+1/3; (viii) −y−1/3, x−y−2/3, z+1/3; (ix) −y, x−y−1, z; (x) −x+y+1, −x+1, z; (xi) x−1, y, z; (xii) x+1, y, z; (xiii) x+1, y+1, z. |