K2Ln2As2Se9 (Ln = Sm, Gd): The First Quaternary Rare-Earth Selenoarsenate Compounds with a 3D Framework Containing Chairlike As2Se4 Units
Yuandong Wu; Wolfgang Bensch; Inorganic Chemistry 48 (2009) 2729–2731; doi:10.1021/ic802368j

data_4301870
_publ_section_title
;
K2Ln2As2Se9 (Ln = Sm, Gd): The First Quaternary Rare-Earth Selenoarsenate
Compounds with a 3D Framework Containing Chairlike As2Se4 Units
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_journal_name_full               'Inorganic Chemistry'
_journal_page_first              2729
_journal_page_last               2731
_journal_paper_doi               10.1021/ic802368j
_journal_volume                  48
_journal_year                    2009
_chemical_formula_moiety         'As2 Se9 Sm2, 2(K)'
_chemical_formula_sum            'As2 K2 Se9 Sm2'
_chemical_formula_weight         1239.40
_chemical_name_systematic
;
 ?
;
_space_group_IT_number           62
_symmetry_cell_setting           orthorhombic
_symmetry_space_group_name_Hall  '-P 2ac 2n'
_symmetry_space_group_name_H-M   'P n m a'
_atom_sites_solution_primary     direct
_atom_sites_solution_secondary   difmap
_audit_creation_method           SHELXL-97
_cell_angle_alpha                90.00
_cell_angle_beta                 90.00
_cell_angle_gamma                90.00
_cell_formula_units_Z            8
_cell_length_a                   17.1739(11)
_cell_length_b                   8.4628(5)
_cell_length_c                   22.6963(15)
_cell_measurement_reflns_used    7998
_cell_measurement_temperature    170(2)
_cell_measurement_theta_max      28.1
_cell_measurement_theta_min      2.4
_cell_volume                     3298.7(4)
_computing_structure_refinement  'SHELXL-97 (Sheldrick, 1997)'
_diffrn_ambient_temperature      170(2)
_diffrn_detector_area_resol_mean 0
_diffrn_measured_fraction_theta_full 0.951
_diffrn_measured_fraction_theta_max 0.958
_diffrn_measurement_device_type  'Stoe Imaging Diffraction System'
_diffrn_measurement_method       '\f scans'
_diffrn_radiation_monochromator  graphite
_diffrn_radiation_source         'fine-focus sealed tube'
_diffrn_radiation_type           MoK\a
_diffrn_radiation_wavelength     0.71073
_diffrn_reflns_av_R_equivalents  0.0712
_diffrn_reflns_av_sigmaI/netI    0.0469
_diffrn_reflns_limit_h_max       22
_diffrn_reflns_limit_h_min       -22
_diffrn_reflns_limit_k_max       11
_diffrn_reflns_limit_k_min       -11
_diffrn_reflns_limit_l_max       29
_diffrn_reflns_limit_l_min       -15
_diffrn_reflns_number            18046
_diffrn_reflns_theta_full        25.00
_diffrn_reflns_theta_max         28.05
_diffrn_reflns_theta_min         2.37
_diffrn_standards_decay_%        0
_diffrn_standards_interval_count 0
_diffrn_standards_interval_time  0
_diffrn_standards_number         0
_exptl_absorpt_coefficient_mu    31.365
_exptl_absorpt_correction_T_max  0.1832
_exptl_absorpt_correction_T_min  0.0399
_exptl_absorpt_correction_type   numerical
_exptl_absorpt_process_details   X-Shape
_exptl_crystal_colour            black
_exptl_crystal_density_diffrn    4.991
_exptl_crystal_density_method    'not measured'
_exptl_crystal_description       needle
_exptl_crystal_F_000             4272
_exptl_crystal_size_max          0.25
_exptl_crystal_size_mid          0.06
_exptl_crystal_size_min          0.01
_refine_diff_density_max         2.228
_refine_diff_density_min         -2.221
_refine_diff_density_rms         0.373
_refine_ls_extinction_coef       0.000120(19)
_refine_ls_extinction_expression Fc^*^=kFc[1+0.001xFc^2^\l^3^/sin(2\q)]^-1/4^
_refine_ls_extinction_method     SHELXL
_refine_ls_goodness_of_fit_ref   0.992
_refine_ls_matrix_type           full
_refine_ls_number_parameters     164
_refine_ls_number_reflns         4090
_refine_ls_number_restraints     0
_refine_ls_restrained_S_all      0.992
_refine_ls_R_factor_all          0.0536
_refine_ls_R_factor_gt           0.0348
_refine_ls_shift/su_max          0.001
_refine_ls_shift/su_mean         0.000
_refine_ls_structure_factor_coef Fsqd
_refine_ls_weighting_details
'calc w=1/[\s^2^(Fo^2^)+(0.0471P)^2^+0.0000P] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.0775
_refine_ls_wR_factor_ref         0.0844
_reflns_number_gt                3095
_reflns_number_total             4090
_reflns_threshold_expression     >2sigma(I)
_cod_data_source_file            ic802368j_si_002_2.cif
_cod_data_source_block           pnma
_cod_database_code               4301870