data_2002896
_journal_name_full     'Acta Crystallographica, Section B'
_journal_year     1998
_journal_volume     B54
_journal_page_first     531
_journal_page_last     546
_publ_section_title
;
Cristobalite-related phases in the NaAlO2-NaAlSiO4 system  I.  Two tetragonal
 and two orthorhombic structures
;
loop_
    _publ_author_name
    'Thompson, John G'
    'Withers, Ray L.'
    'Melnitchenko, Alexandra'
    'Palethorpe, Stephen R.'
_chemical_formula_sum     'Na1.15 Al1.15 Si0.85 O4'
_chemical_formula_weight     145.34
_symmetry_space_group_name_H-M     'P b 21 a'
loop_
    _symmetry_equiv_pos_as_xyz
    'x,y,z'
    '-x,y+1/2,-z'
    'x+1/2,y,-z'
    '1/2-x,1/2+y,z'
_cell_length_a     10.214(2)
_cell_length_b     14.226(7)
_cell_length_c     10.3080(10)
_cell_angle_alpha     90.0
_cell_angle_beta     90.0
_cell_angle_gamma     90.0
_cell_volume     1497.9(3)
_cell_formula_units_Z     16
_cell_measurement_temperature     293
_exptl_crystal_density_diffrn     2.578
_diffrn_ambient_temperature     293
_diffrn_radiation_type     'Cu K\a'
_diffrn_radiation_wavelength     1.5418
_diffrn_radiation_source     'sealed tube'
_diffrn_radiation_monochromator     'graphite'
_diffrn_measurement_device     'Siemens D-5000'
_diffrn_measurement_method     'profile data from theta/2theta scan'
loop_
    _atom_site_label
    _atom_site_fract_x
    _atom_site_fract_y
    _atom_site_fract_z
    _atom_site_U_iso_or_equiv
    _atom_site_occupancy
    _atom_site_type_symbol
    M1 0.995(2) 0.001(3) 0.024(2) 0.575 0.033(2) Al
    M1 0.995(2) 0.001(3) 0.024(2) 0.425 0.033(2) Si
    M2 0.996(2) -0.002(3) 0.5230(10)
                                   0.575 0.033(2) Al
    M2 0.996(2) -0.002(3) 0.5230(10)
                                   0.425 0.033(2) Si
    M3 0.267(2) 0.245(3) 0.775(2) 0.575 0.033(2) Al
    M3 0.267(2) 0.245(3) 0.775(2) 0.425 0.033(2) Si
    M4 0.279(2) 0.250(3) 0.274(2) 0.575 0.033(2) Al
    M4 0.279(2) 0.250(3) 0.274(2) 0.425 0.033(2) Si
    M5 0.243(2) 0.126(3) 0.0290(10)
                                  0.575 0.033(2) Al
    M5 0.243(2) 0.126(3) 0.0290(10)
                                  0.425 0.033(2) Si
    M6 0.246(2) 0.120(3) 0.5190(10)
                                  0.575 0.033(2) Al
    M6 0.246(2) 0.120(3) 0.5190(10)
                                  0.425 0.033(2) Si
    M7 0.9750(10)
                0.872(3) 0.772(2) 0.575 0.033(2) Al
    M7 0.9750(10)
                0.872(3) 0.772(2) 0.425 0.033(2) Si
    M8 0.9780(10)
                0.877(3) 0.275(2) 0.575 0.033(2) Al
    M8 0.9780(10)
                0.877(3) 0.275(2) 0.425 0.033(2) Si
    Na1 0.496(14) 0.243(7) 0.039(8) 1.0 0.077(10) Na
    Na2 0.500 0.250 0.500 0.15 0.077(10) Na
    Na3 0.750 0.500 0.250 0.15 0.077(10) Na
    Na4 0.757(14) 0.493(12) 0.234(6) 1.0 0.077(10) Na
    Na5 0.750 0.375 0.000 0.15 0.077(10) Na
    Na6 0.775(9) 0.375(7) 0.486(7) 1.0 0.077(10) Na
    Na7 -0.013(15) 0.617(13) 0.733(9) 1.0 0.077(10) Na
    Na8 0.000 0.625 0.250 0.15 0.077(10) Na
    O1 0.149(2) 0.034(3) -0.004(2) 1.0 0.028(2) O
    O2 0.089(2) 0.091(3) 0.487(2) 1.0 0.028(2) O
    O3 0.422(2) 0.281(3) 0.780(3) 1.0 0.028(2) O
    O4 0.420(2) 0.293(3) 0.221(2) 1.0 0.028(2) O
    O5 -0.042(2) -0.088(3) -0.076(2) 1.0 0.028(2) O
    O6 0.029(2) -0.089(3) 0.421(2) 1.0 0.028(2) O
    O7 0.256(3) 0.153(3) 0.675(3) 1.0 0.028(2) O
    O8 0.220(2) 0.166(3) 0.178(2) 1.0 0.028(2) O
    O9 0.899(2) 0.093(3) -0.006(2) 1.0 0.028(2) O
    O10 0.840(2) 0.026(3) 0.505(2) 1.0 0.028(2) O
    O11 0.173(2) 0.333(3) 0.718(3) 1.0 0.028(2) O
    O12 0.171(2) 0.339(3) 0.282(3) 1.0 0.028(2) O
    O13 0.029(2) -0.042(3) 0.673(2) 1.0 0.028(2) O
    O14 -0.023(2) -0.030(3) 0.178(2) 1.0 0.028(2) O
    O15 0.219(3) 0.214(3) 0.924(3) 1.0 0.028(2) O
    O16 0.290(2) 0.209(3) 0.425(2) 1.0 0.028(2) O