Li~2~PbGeS~4~ and Li~2~EuGeS~4~: polar chalcopyrites with a severe tetragonal compression
Aitken, Jennifer A.; Larson, Paul; Mahanti, S. D.; Kanatzidis, Mercouri G.; Chemistry of Materials 13 (2001) 4714–4721; doi:10.1021/cm0105357

data_4002652
_publ_section_title
;
 Li~2~PbGeS~4~ and Li~2~EuGeS~4~: polar chalcopyrites with a severe
 tetragonal compression
;
_journal_coden_ASTM              CMATEX
_journal_issue                   12
_journal_name_full               'Chemistry of Materials'
_journal_page_first              4714
_journal_page_last               4721
_journal_paper_doi               10.1021/cm0105357
_journal_volume                  13
_journal_year                    2001
_chemical_formula_sum            'Ge Li2 Pb S4'
_chemical_formula_weight         421.90
_space_group_crystal_system      tetragonal
_space_group_IT_number           121
_space_group_name_Hall           'I -4 2'
_space_group_name_H-M_alt        'I -4 2 m'
_atom_sites_solution_hydrogens   geom
_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            2
_cell_length_a                   6.5224(5)
_cell_length_b                   6.5224(5)
_cell_length_c                   7.7603(8)
_cell_measurement_reflns_used    4391
_cell_measurement_temperature    293(2)
_cell_measurement_theta_max      26.97
_cell_volume                     330.14(5)
_computing_cell_refinement       saint
_computing_data_collection       smart
_computing_data_reduction        saint
_computing_structure_refinement  'SHELXL-97 (Sheldrick, 1997)'
_computing_structure_solution    'SHELXS-97 (Sheldrick, 1990)'
_diffrn_ambient_temperature      293(2)
_diffrn_measured_fraction_theta_full 1.000
_diffrn_measured_fraction_theta_max 1.000
_diffrn_measurement_device_type  'Bruker Smart Platform CCD'
_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  0.0826
_diffrn_reflns_av_sigmaI/netI    0.0415
_diffrn_reflns_limit_h_max       7
_diffrn_reflns_limit_h_min       -8
_diffrn_reflns_limit_k_max       8
_diffrn_reflns_limit_k_min       -8
_diffrn_reflns_limit_l_max       9
_diffrn_reflns_limit_l_min       -9
_diffrn_reflns_number            1626
_diffrn_reflns_theta_full        26.97
_diffrn_reflns_theta_max         26.97
_diffrn_reflns_theta_min         4.08
_exptl_absorpt_coefficient_mu    31.146
_exptl_absorpt_correction_T_max  1.000000
_exptl_absorpt_correction_T_min  0.357802
_exptl_absorpt_correction_type   empirical
_exptl_absorpt_process_details   Sadabs
_exptl_crystal_colour            yellow
_exptl_crystal_density_diffrn    4.244
_exptl_crystal_density_method    'not measured'
_exptl_crystal_description       plate-like
_exptl_crystal_F_000             368
_exptl_crystal_size_max          0.26
_exptl_crystal_size_mid          0.14
_exptl_crystal_size_min          0.05
_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         1.541
_refine_diff_density_min         -1.476
_refine_diff_density_rms         0.289
_refine_ls_abs_structure_details 'Flack H D (1983), Acta Cryst. A39, 876-881'
_refine_ls_abs_structure_Flack   0.09(2)
_refine_ls_extinction_coef       0.072(6)
_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   1.114
_refine_ls_hydrogen_treatment    mixed
_refine_ls_matrix_type           full
_refine_ls_number_parameters     14
_refine_ls_number_reflns         203
_refine_ls_number_restraints     0
_refine_ls_restrained_S_all      1.114
_refine_ls_R_factor_all          0.0253
_refine_ls_R_factor_gt           0.0253
_refine_ls_shift/su_max          0.000
_refine_ls_shift/su_mean         0.000
_refine_ls_structure_factor_coef Fsqd
_refine_ls_weighting_details
'calc w=1/[\s^2^(Fo^2^)+(0.0399P)^2^+0.0000P] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.0646
_refine_ls_wR_factor_ref         0.0646
_refine_special_details
; 
 Refinement of F^2^ against ALL reflections.  The weighted R-factor wR and 
 goodness 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 threshold expression of 
 F^2^ > 2sigma(F^2^) is used only for calculating R-factors(gt) 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_gt                203
_reflns_number_total             203
_reflns_threshold_expression     >2sigma(I)
_cod_data_source_file            cm0105357_si_001.cif
_cod_data_source_block           Li2PbGeS4
_cod_database_code               4002652