The crystal structures of NaNO3 at 100 K, 120 K and 563 K

NaNO3, Synchrotron X-ray diffraction at 100 K: λ = 0.56Å, R-3c, a = 5.0655(5) Å, c = 16.577(3) Å, V = 368.4 Å3, Z = 6, F(000) = 78e, refinement on |F|. Anharmonic motion of N and O up to the fourth order of a Gram-Charlier expansion and multipoles for all ions were refined. R = 0.029, w R = 0.028, S 2 = 3.539, 369 unique intensities, 41 parameters. Neutron diffraction at 120 K: λ = 0.87 Å, R-3c, a = 5.0660(5) Å, c = 16.593(3) Å, V = 368.8 Å3, Z = 6, F(000) = 182.1 fm. Two data sets from two crystals of different sizes have been used, one with 187, the other with 165 unique intensities. Refinement on |F|2 including weak and negative intensities. Anharmonic motion of N and O up to the fourth order of a Gram-Charlier expansion was refined R = 0.112, w R = 0.080, S 2 = 3.499, 205 unique intensities, 35 parameters. Neutron diffraction at 563 K: λ = 0.92 Å, R-3m, a = 5.0889 (5) Å, c = 8.868(3) Å, V = 204.6 Å3, Z = 3, F(000) = 91.05e, refinement on |F|2 including weak and negative intensities. R = 0.031, w R = 0.017, S 2 = 1.714, 84 unique intensities, 16 refined parameters. At 100 K multipolar expansion of the electron density reveals bonding electrons and a strong deformation of the atoms within the planar NO3-group much clearer than at room temperature. At 563 K strongly anharmonic thermal displacement factors are found.