KAlAs~2~O~7~
Boughzala, Habib; Jouini, Tahar; Acta Crystallographica, Section C: Crystal Structure Communications 51 (1995) 179–181; doi:10.1107/S0108270194010395

data_2003216
_publ_section_title
;
 KAlAs~2~O~7~
;
_journal_coden_ASTM              ACSCEE
_journal_coeditor_code           NA1114
_journal_issue                   2
_journal_name_full
;
 Acta Crystallographica, Section C: Crystal Structure Communications
;
_journal_page_first              179
_journal_page_last               181
_journal_paper_doi               10.1107/S0108270194010395
_journal_volume                  51
_journal_year                    1995
_chemical_formula_moiety         'K Al As2 O7'
_chemical_formula_structural     'K Al (As2 O7)'
_chemical_formula_sum            'Al As2 K O7'
_chemical_formula_weight         327.92
_chemical_name_systematic        'aluminium potassium diarsenate'
_space_group_crystal_system      triclinic
_space_group_IT_number           2
_space_group_name_Hall           '-P 1'
_space_group_name_H-M_alt        'P -1'
_atom_sites_solution_primary     heavy
_audit_creation_method           SHELXL
_cell_angle_alpha                96.600(8)
_cell_angle_beta                 104.517(8)
_cell_angle_gamma                102.864(7)
_cell_formula_units_Z            2
_cell_length_a                   6.192(4)
_cell_length_b                   6.297(3)
_cell_length_c                   8.1060(10)
_cell_measurement_reflns_used    25
_cell_measurement_temperature    293(2)
_cell_measurement_theta_max      16
_cell_measurement_theta_min      14
_cell_volume                     293.4(2)
_computing_cell_refinement       'CAD4 Software (Enraf-Nonius, 1989)'
_computing_data_collection       'CAD4 Software (Enraf-Nonius, 1989)'
_computing_data_reduction        'MOLEN (Fair, 1990)'
_computing_structure_refinement  'SHELXL93 (Sheldrick, 1993)'
_computing_structure_solution    'SHELXS86 (Sheldrick, 1990)'
_diffrn_ambient_temperature      293(2)
_diffrn_measurement_device       'Enraf-Nonius CAD-4'
_diffrn_measurement_method       \w/2\q
_diffrn_radiation_monochromator  graphite
_diffrn_radiation_source         'fine-focus sealed tube'
_diffrn_radiation_type           MoK\a
_diffrn_radiation_wavelength     0.71069
_diffrn_reflns_av_R_equivalents  0.0094
_diffrn_reflns_av_sigmaI/netI    0.0554
_diffrn_reflns_limit_h_max       7
_diffrn_reflns_limit_h_min       -7
_diffrn_reflns_limit_k_max       7
_diffrn_reflns_limit_k_min       -7
_diffrn_reflns_limit_l_max       9
_diffrn_reflns_limit_l_min       0
_diffrn_reflns_number            1057
_diffrn_reflns_theta_max         24.93
_diffrn_reflns_theta_min         3.37
_diffrn_standards_decay_%        0.66
_diffrn_standards_interval_time  120
_diffrn_standards_number         2
_exptl_absorpt_coefficient_mu    12.234
_exptl_absorpt_correction_T_max  1.0000
_exptl_absorpt_correction_T_min  0.9986
_exptl_absorpt_correction_type   sphere
_exptl_crystal_colour            colourless
_exptl_crystal_density_diffrn    3.712
_exptl_crystal_description       tablets
_exptl_crystal_F_000             308
_exptl_crystal_size_max          0.08
_exptl_crystal_size_mid          0.07
_exptl_crystal_size_min          0.006
_exptl_special_details
;
Background counts by usual scan on each side of the reflection
;
_geom_special_details
;
 All esds (except the esd in the dihedral angle between two l.s. planes)
 are estimated using the full covariance matrix.  The cell esds are taken
 into account individually in the estimation of esds in distances, angles
 and torsion angles; correlations between esds in cell parameters are only
 used when they are defined by crystal symmetry.  An approximate (isotropic)
 treatment of cell esds is used for estimating esds involving l.s. planes.
;
_refine_diff_density_max         1.570
_refine_diff_density_min         -1.871
_refine_ls_extinction_coef       0.019(3)
_refine_ls_extinction_expression
'F~c~^*^ = kF~c~[1+0.001xF~c~^2^\l^3^/sin(2\q)]^-1/4^'
_refine_ls_extinction_method     SHELXL93
_refine_ls_goodness_of_fit_all   0.537
_refine_ls_goodness_of_fit_obs   0.555
_refine_ls_matrix_type           full
_refine_ls_number_parameters     104
_refine_ls_number_reflns         983
_refine_ls_number_restraints     0
_refine_ls_restrained_S_all      0.537
_refine_ls_restrained_S_obs      0.555
_refine_ls_R_factor_all          0.0353
_refine_ls_R_factor_obs          0.0331
_refine_ls_shift/esd_max         0.000
_refine_ls_shift/esd_mean        0.000
_refine_ls_structure_factor_coef Fsqd
_refine_ls_weighting_details
;
w = 1/[\s^2^(F~o~^2^) + (0.1264P)^2^ + 4.1692P] where
P = (F~o~^2^ + 2F~c~^2^)/3
;
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_all         0.0902
_refine_ls_wR_factor_obs         0.0879
_refine_special_details
;
 Refinement on F~2~ for ALL reflections except for 0 with very negative F~2~
 or flagged by the user for potential systematic errors.  Weighted R-factors
 wR and all goodnesses of fit S are based on F~2~, conventional R-factors R
 are based on F, with F set to zero for negative F~2~. The observed criterion
 of F~2~ > 2sigma(F~2~) is used only for calculating _R_factor_obs etc. and is
 not relevant to the choice of reflections for refinement.  R-factors based
 on F~2~ are statistically about twice as large as those based on F, and R-
 factors based on ALL data will be even larger.
;
_reflns_number_observed          883
_reflns_number_total             983
_reflns_observed_criterion       >2\s(I)
_cod_depositor_comments
;
 Added additional information after consulting the supplementary material
 of the original publication.

 Antanas Vaitkus,
 2020-03-18
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_cod_database_code               2003216