A closer look into close packing: pentacoordinated silicon in a high-pressure polymorph of danburite
Pakhomova, Anna; Bykova, Elena; Bykov, Maxim; Glazyrin, Konstantin; Gasharova, Biliana; Liermann, Hanns-Peter; Mezouar, Mohamed; Gorelova, Liudmila; Krivovichev, Sergey; Dubrovinsky, Leonid; IUCrJ 4 (2017) –; doi:10.1107/S2052252517010612

data_1546776
_publ_section_title
;
 A closer look into close packing: pentacoordinated silicon in a
 high-pressure polymorph of danburite
;
_journal_issue                   5
_journal_name_full               IUCrJ
_journal_page_first
;
;
_journal_paper_doi               10.1107/S2052252517010612
_journal_volume                  4
_journal_year                    2017
_chemical_formula_moiety         'B2 Ca O8 Si2'
_chemical_formula_sum            'B2 Ca O8 Si2'
_chemical_formula_weight         245.88
_chemical_name_common            danburite
_chemical_name_systematic        danburite
_space_group_crystal_system      orthorhombic
_space_group_IT_number           62
_space_group_name_Hall           '-P 2c 2n'
_space_group_name_H-M_alt        'P n a m'
_symmetry_space_group_name_Hall  '-P 2c 2n'
_symmetry_space_group_name_H-M   'P n a m'
_audit_creation_method           SHELXL-2014/7
_cell_angle_alpha                90
_cell_angle_beta                 90
_cell_angle_gamma                90
_cell_formula_units_Z            4
_cell_length_a                   6.3537(5)
_cell_length_b                   7.9518(3)
_cell_length_c                   8.0112(3)
_cell_measurement_pressure       25400000
_cell_measurement_reflns_used    977
_cell_measurement_temperature    293(2)
_cell_measurement_theta_max      16.6370
_cell_measurement_theta_min      1.6750
_cell_volume                     404.75(4)
_computing_cell_refinement
;
CrysAlisPro, Agilent Technologies,
Version 1.171.36.28 (release 01-02-2013 CrysAlis171 .NET)
(compiled Feb  1 2013,16:14:44)
;
_computing_data_collection
;
CrysAlisPro, Agilent Technologies,
Version 1.171.36.28 (release 01-02-2013 CrysAlis171 .NET)
(compiled Feb  1 2013,16:14:44)
;
_computing_data_reduction
;
CrysAlisPro, Agilent Technologies,
Version 1.171.36.28 (release 01-02-2013 CrysAlis171 .NET)
(compiled Feb  1 2013,16:14:44)
;
_computing_structure_refinement  'SHELXL-2014/7 (Sheldrick, 2014)'
_computing_structure_solution    'SHELXL-2014/7 (Sheldrick, 2014)'
_diffrn_ambient_pressure         25400000
_diffrn_ambient_temperature      293(2)
_diffrn_measured_fraction_theta_full 0.796
_diffrn_measured_fraction_theta_max 0.515
_diffrn_measurement_device_type
'esperanto-CrysAlisPro-abstract goniometer imported esperanto images'
_diffrn_measurement_method       '\w scans'
_diffrn_radiation_type           synchrotron
_diffrn_radiation_wavelength     0.29056
_diffrn_reflns_av_R_equivalents  0.0239
_diffrn_reflns_av_unetI/netI     0.0291
_diffrn_reflns_Laue_measured_fraction_full 0.796
_diffrn_reflns_Laue_measured_fraction_max 0.515
_diffrn_reflns_limit_h_max       9
_diffrn_reflns_limit_h_min       -10
_diffrn_reflns_limit_k_max       12
_diffrn_reflns_limit_k_min       -13
_diffrn_reflns_limit_l_max       14
_diffrn_reflns_limit_l_min       -15
_diffrn_reflns_number            2163
_diffrn_reflns_point_group_measured_fraction_full 0.796
_diffrn_reflns_point_group_measured_fraction_max 0.515
_diffrn_reflns_theta_full        10.500
_diffrn_reflns_theta_max         16.730
_diffrn_reflns_theta_min         1.677
_diffrn_source                   synchrotron
_diffrn_source_type              'PETRA III, Beamline P02.2'
_exptl_absorpt_coefficient_mu    0.215
_exptl_crystal_colour            colorless
_exptl_crystal_density_diffrn    4.035
_exptl_crystal_description       'plate crystal'
_exptl_crystal_F_000             488
_exptl_crystal_size_max          0.020
_exptl_crystal_size_mid          0.015
_exptl_crystal_size_min          0.010
_refine_diff_density_max         1.049
_refine_diff_density_min         -1.441
_refine_diff_density_rms         0.280
_refine_ls_extinction_coef       0.18(5)
_refine_ls_extinction_expression Fc^*^=kFc[1+0.001xFc^2^\l^3^/sin(2\q)]^-1/4^
_refine_ls_extinction_method     'SHELXL-2014/7 (Sheldrick 2014'
_refine_ls_goodness_of_fit_ref   1.321
_refine_ls_hydrogen_treatment    undef
_refine_ls_matrix_type           full
_refine_ls_number_parameters     65
_refine_ls_number_reflns         891
_refine_ls_number_restraints     0
_refine_ls_restrained_S_all      1.321
_refine_ls_R_factor_all          0.0596
_refine_ls_R_factor_gt           0.0423
_refine_ls_shift/su_max          0.000
_refine_ls_shift/su_mean         0.000
_refine_ls_structure_factor_coef Fsqd
_refine_ls_weighting_details
'w=1/[\s^2^(Fo^2^)+(0.0923P)^2^+0.4473P] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.1256
_refine_ls_wR_factor_ref         0.1783
_reflns_Friedel_coverage         0.000
_reflns_number_gt                742
_reflns_number_total             891
_reflns_threshold_expression     'I > 2\s(I)'
_cod_data_source_file            lt5006.cif
_cod_data_source_block           danburite_25.4GPa
_cod_database_code               1546776
_shelx_shelxl_version_number     2014/7
_shelx_res_checksum              85454
_shelx_hkl_checksum              46152