Pyroelectric Ba(NO2)2⋅H2O: Room temperature crystal structure

Abstract

Barium nitrite monohydrate, Ba(NO2)2⋅H2O, is strongly pyroelectric at room temperature and crystallizes in the hexagonal system with space group P65, or the enantiomorphous P61, and with six formulas in the unit cell. The lattice constants at 298 K are a=7.074 90±0.000 03 and c=17.890 87±0.000 12 Å (λCuKα1=1.540598 Å). The integrated intensities of most reflections within a quadrant of reciprocal space having radius (sinϑ)/λ?1.15 or 1.08 Å−1 were measured on two different crystals, each with different diffractometer, resulting in 3218 Fmeas for one set and 3671 Fmeas for the second set of independent structure factors. The crystal structure was solved from Patterson and Fourier series, and refined by the method of least squares. The final agreement factor R=0.026 for the first set, 0.018 for the second set of Fmeas. The two sets of Fmeas and the derived structural parameters are compared using normal probability plot analysis. The two NO−2 ions have a mean N–O distance of 1.246±0.002 Å and O–N–O angle of 114.2±0.2°. The Ba2+ ion is coordinated by nine oxygen and one nitrogen atoms at an average distance of 2.899 Å. The water molecule has a weighted mean O–H distance of 1.04±0.03 Å and H–O–H angle of 102.7°±4.3°: it is hydrogen bonded to two independent NO−2 ions by an O–H⋅⋅⋅O bond of 2.878 Å and an O–H⋅⋅⋅N bond of 2.951 Å.