data_2003130
_journal_name_full     'Acta Crystallographica, Section B'
_journal_year     1999
_journal_volume     B55
_journal_page_first     273
_journal_page_last     284
_publ_section_title
;
Electron Density Distribution and Madelung Potential in \a-Spodumene
 LiAl(SiO~3~)~2~ from Two Wavelengths High Resolution X-Ray Diffraction
 Data
;
loop_
    _publ_author_name
    'Kuntzinger, Sandrine'
    'Ghermani, Nour Eddine'
_chemical_formula_moiety     ?
_chemical_formula_sum     'Al Li O6 Si2'
_chemical_formula_iupac     'Li Al (Si O3)2'
_chemical_formula_weight     186.09
_symmetry_cell_setting     monoclinic
_symmetry_space_group_name_H-M     'C 1 2/c 1'
loop_
    _symmetry_equiv_pos_as_xyz
    'x, y, z'
    'x+1/2, y+1/2, z'
    '-x, y, -z+1/2'
    '-x+1/2, y+1/2, -z+1/2'
    '-x, -y, -z'
    'x, -y, z+1/2'
    '-x+1/2, -y+1/2, -z'
    'x+1/2, 1/2-y, z+1/2'
_cell_length_a     9.4560(10)
_cell_length_b     8.3860(10)
_cell_length_c     5.2160(10)
_cell_angle_alpha     90.00
_cell_angle_beta     110.130(10)
_cell_angle_gamma     90.00
_cell_volume     388.36(9)
_cell_formula_units_Z     4
_cell_measurement_reflns_used     25
_cell_measurement_theta_min     9.4
_cell_measurement_theta_max     23.6
_cell_measurement_temperature     293
_exptl_crystal_description     Parallelepiped
_exptl_crystal_colour     Colourless
_exptl_crystal_size_max     .36
_exptl_crystal_size_mid     .18
_exptl_crystal_size_min     .06
_exptl_crystal_size_rad     ?
_exptl_crystal_density_diffrn     3.18
_exptl_crystal_density_meas     ?
_exptl_crystal_density_method     'not measured'
_exptl_crystal_F_000     368.0
_exptl_absorpt_coefficient_mu     .54
loop_
    _exptl_absorpt_correction_type
    _exptl_absorpt_process_details
    integration '(ABSORB, G. de Titta, 1985)'
    empirical '(DREADD, R. Blessing, 1995)'
_exptl_absorpt_correction_T_min     .82
_exptl_absorpt_correction_T_max     .97
_diffrn_radiation_type     'Ag K\a'
_diffrn_radiation_wavelength     0.5608
_diffrn_measurement_device     'Enraf-Nonius CAD4 diffractometer'
_diffrn_measurement_method     '\w/2\q scans'
_diffrn_detector_area_resol_mean     ?
_diffrn_reflns_number     15850
_diffrn_reflns_av_R_equivalents     0.0210
_diffrn_reflns_theta_min     2.6
_diffrn_reflns_theta_max     45.0
_diffrn_reflns_theta_full     45.0
_diffrn_measured_fraction_theta_max     .93
_diffrn_measured_fraction_theta_full     .93
_diffrn_reflns_limit_h_min     -23
_diffrn_reflns_limit_h_max     23
_diffrn_reflns_limit_k_min     -21
_diffrn_reflns_limit_k_max     21
_diffrn_reflns_limit_l_min     -13
_diffrn_reflns_limit_l_max     13
_diffrn_standards_number     4
_diffrn_standards_interval_time     120
_diffrn_standards_decay_%     0
_reflns_number_total     3241
_reflns_number_gt     2261
_reflns_threshold_expression     I>3\s(I)
_refine_ls_structure_factor_coef     F
_refine_ls_R_factor_gt     .0155
_refine_ls_wR_factor_ref     .0151
_refine_ls_goodness_of_fit_ref     .84
_refine_ls_number_reflns     2261
_refine_ls_number_parameters     138
_refine_ls_weighting_scheme     calc
_refine_ls_weighting_details     'w=1/[\s^2^(F^2^)+(0.0160F^2^)^2^]'
_refine_ls_shift/su_max     0.0
_refine_diff_density_max     0.2
_refine_diff_density_min     -0.1
loop_
    _refine_ls_extinction_method
    'Becker-Coppens type 1 Lorentzian isotropic'
_refine_ls_extinction_coef     4.9.10^2^
_refine_ls_abs_structure_details     ?
_refine_ls_abs_structure_Flack     ?
loop_
    _atom_type_symbol
    _atom_type_description
    _atom_type_scat_dispersion_real
    _atom_type_scat_dispersion_imag
    _atom_type_scat_source
    'Si' 'Si' .0522 .0431
                         'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4'
    'Al' 'Al' .0406 .0313
                         'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4'
    'O' 'O' .0056 .0036 'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4'
    'Li' 'Li' -.0004 .0000
                         'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4'
loop_
    _atom_site_label
    _atom_site_fract_x
    _atom_site_fract_y
    _atom_site_fract_z
    _atom_site_U_iso_or_equiv
    _atom_site_thermal_displace_type
    _atom_site_type_symbol
    Si 0.294100(10)
                  0.093450(10)
                             0.25593(2) 0.00397(3) Uani Si
    Al 0.00000 0.90669(2) 0.25000 0.00424(4) Uani Al
    O~1~ 0.10975(2) 0.08237(2) 0.14061(4) 0.00495(5) Uani O
    O~2~ 0.36470(3) 0.26708(3) 0.30050(5) 0.00771(6) Uani O
    O~3~ 0.35663(2) 0.98668(3) 0.05824(4) 0.00766(6) Uani O
    Li 0.00000 0.27494(14) 0.25000 0.01474(4) Uani Li
loop_
    _atom_site_aniso_label
    _atom_site_aniso_U_11
    _atom_site_aniso_U_22
    _atom_site_aniso_U_33
    _atom_site_aniso_U_12
    _atom_site_aniso_U_13
    _atom_site_aniso_U_23
    Si 0.00386(3) 0.00447(3) 0.00355(3) -0.00062(2) 0.00125(2) -0.00020(2)
    Al 0.00420(4) 0.00427(4) 0.00418(4) 0.00000 0.00134(3) 0.00000
    O~1~ 0.00389(5) 0.00587(6) 0.00469(6) -0.00033(5) 0.00096(4) 0.00020(5)
    O~2~ 0.00817(7) 0.00569(6) 0.00991(7) -0.00291(5) 0.00392(6) -0.00084(6)
    O~3~ 0.00590(6) 0.01141(8) 0.00529(6) 0.00068(6) 0.00145(5) -0.00339(6)
    Li 0.0154(5)   0.0137(5)   0.0151(5)   0.00000 0.0051(4)   0.00000