Anharmonic motion and multipolar expansion of the electron density in NaNO3

Abstract

Abstract NaNO3, R[unk]c, a = 5.0701(2) Å, c = 16.822(2) Å, V = 374.4 Å3, Z = 6. Neutron diffraction: λ = 0.87013 Å, μ = 0.1 cm−1, F(000) = 182.1 fm. The intensities are checked for normal and independent distribution and their Poisson variances are modified with the aid of χ 2 values of repeatedly measured intensities. Refinement on |F|2 including weak and negative intensities. Anharmonic motion of N and O up the third order of a Gram-Charlier expansion was refined. R = 0.032, wR = 0.026, S 2 = 1.99, 3642 measured and 317 unique intensities, 17 parameters. Synchrotron X-ray diffraction: λ = 0.56 Å, F(000) = 78e, refinement on |F|. Anharmonic motion of N and O up to the fourth order of a Gram-Charlier expansion was refined. R = 0.020, wR = 0.007, S 2 = 1.51,443 unique intensities, 39 parameters. No ±180° Ising-type in plane orientational disorder of NO3-groups is observed at 293 K. Multipolar expansion of the electron density reveals bonding electrons and a strong deformation of the atoms within the planar NO3-group.