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

NaNO3, Synchrotron X-ray diffraction at 100 K: lambda = 0.56 Angstrom, R (3) over barc, a = 5.0655(5) Angstrom, c = 16.577(3) Angstrom, V = 368.4 Angstrom (3), 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, wR=0.028, S-2 = 3.539, 369 unique intensities, 41 parameters. Neutron diffraction at 120 K: lambda = 0.87 Angstrom, R (3) over barc, a = 5.0660(5) Angstrom, c = 16.593(3) Angstrom, lambda = 368.8 Angstrom (3), 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, wR=0.080, S-2 = 3.499, 205 unique intensities, 35 parameters. Neutron diffraction at 563 K: lambda = 0.92 Angstrom, R (3) over barm, a = 5.0889(5) Angstrom, c = 8.868(3) Angstrom, V = 204.6 Angstrom (3), Z=3, F(000) = 91.05e, refinement on \F\(2) including weak and negative intensities. R = 0.031, wR = 0.017, S-2 = 1.714, 84 unique intensities, 16 refined para meters. 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.