caa a22 4500 463217357 CHVBK 20180405153201.0 cr unu---uuuuu 170326e20071201xx s 000 0 eng 10.1007/s00269-007-0188-0 doi (NATIONALLICENCE)springer-10.1007/s00269-007-0188-0 A powder neutron diffraction study of the crystal structure of the fluoroperovskite NaMgF3 (neighborite) from 300 to 3.6K [Elektronische Daten] [Roger Mitchell, Malcolm Alexander, Lachlan Cranswick, Ian Swainson] The cell dimensions and crystal structures of the fluoroperovskite NaMgF3 (neighborite), synthesized by solid state methods, have been determined by powder neutron diffraction and Rietveld refinement over the temperature range 300-3.6K using Pt metal as an internal standard for calibration of the neutron wavelength. These data show that Pbnm NaMgF3 does not undergo any phase transitions to structures of lower symmetry with decreasing temperature. The cell dimensions and atomic coordinates together with polyhedron volumes and distortion indices are given for Pbnm NaMgF3 at 25K intervals from 300 to 3.6K. Decreases in the a and c cell dimensions reach a saturation point at 50K, whereas the b dimension becomes saturated at 150K. The distortion of the structure of Pbnm NaMgF3 from the aristotype cubic $$ Pm\ifmmode\expandafter\bar\else\expandafter\=\fi{3}m $$ structure is described in terms of the tilting of the MgF6 octahedra according to the tilt scheme a − a − c + . With decreasing temperature the antiphase tilt (a −) increases from 14.24° to 15.39°, whereas the in-phase tilt (c + ) remains effectively constant at ∼10.7°. Changes in the tilt angles are insufficient to cause changes in the coordination sphere of Na that might induce a low temperature phase transition. The structure of Pbnm NaMgF3 is also described in terms of normal mode analysis and displacements of the condensed normal modes are compared with those of Pbnm KCaF3. Springer-Verlag, 2007 Mitchell Roger Department of Geology, Lakehead University, P7B 5E1, Thunder Bay, ON, Canada aut Alexander Malcolm Department of Geology, Lakehead University, P7B 5E1, Thunder Bay, ON, Canada aut Cranswick Lachlan Chalk River Laboratories, National Research Council of Canada, Neutron Program for Materials Research, Steacie Institute for Molecular Sciences, Building 459, Station 18, K0J 1J0, Chalk River, ON, Canada aut Swainson Ian Chalk River Laboratories, National Research Council of Canada, Neutron Program for Materials Research, Steacie Institute for Molecular Sciences, Building 459, Station 18, K0J 1J0, Chalk River, ON, Canada aut Physics and Chemistry of Minerals Springer-Verlag 34/10(2007-12-01), 705-712 0342-1791 34:10<705 2007 34 269 https://doi.org/10.1007/s00269-007-0188-0 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s00269-007-0188-0 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Mitchell Roger Department of Geology, Lakehead University, P7B 5E1, Thunder Bay, ON, Canada aut NATIONALLICENCE 700 1- Alexander Malcolm Department of Geology, Lakehead University, P7B 5E1, Thunder Bay, ON, Canada aut NATIONALLICENCE 700 1- Cranswick Lachlan Chalk River Laboratories, National Research Council of Canada, Neutron Program for Materials Research, Steacie Institute for Molecular Sciences, Building 459, Station 18, K0J 1J0, Chalk River, ON, Canada aut NATIONALLICENCE 700 1- Swainson Ian Chalk River Laboratories, National Research Council of Canada, Neutron Program for Materials Research, Steacie Institute for Molecular Sciences, Building 459, Station 18, K0J 1J0, Chalk River, ON, Canada aut NATIONALLICENCE 773 0- Physics and Chemistry of Minerals Springer-Verlag 34/10(2007-12-01), 705-712 0342-1791 34:10<705 2007 34 269 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer