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_1546778
_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 Ca1 O8 Si2'
_chemical_formula_sum            'B4 Ca2 O16 Si4'
_chemical_formula_weight         491.76
_chemical_name_common            danburite
_chemical_name_systematic        danburite
_space_group_crystal_system      monoclinic
_space_group_IT_number           14
_space_group_name_Hall           '-P 2ybc'
_space_group_name_H-M_alt        'P 1 21/c 1'
_symmetry_space_group_name_Hall  '-P 2ybc'
_symmetry_space_group_name_H-M   'P 1 21/c 1'
_audit_creation_method           SHELXL-2014/7
_cell_angle_alpha                90
_cell_angle_beta                 89.75(3)
_cell_angle_gamma                90
_cell_formula_units_Z            2
_cell_length_a                   7.9989(17)
_cell_length_b                   7.8697(14)
_cell_length_c                   6.249(3)
_cell_measurement_pressure       32300000
_cell_measurement_reflns_used    326
_cell_measurement_temperature    293(2)
_cell_measurement_theta_max      10.4260
_cell_measurement_theta_min      1.6950
_cell_volume                     393.4(2)
_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         32300000
_diffrn_ambient_temperature      293(2)
_diffrn_measured_fraction_theta_full 0.663
_diffrn_measured_fraction_theta_max 0.657
_diffrn_measurement_device_type
'esperanto-CrysAlisPro-abstract goniometer imported esperanto images'
_diffrn_measurement_method       '\w scans'
_diffrn_radiation_type           synchrotron
_diffrn_radiation_wavelength     0.29024
_diffrn_reflns_av_R_equivalents  0.0536
_diffrn_reflns_av_unetI/netI     0.0587
_diffrn_reflns_Laue_measured_fraction_full 0.663
_diffrn_reflns_Laue_measured_fraction_max 0.657
_diffrn_reflns_limit_h_max       9
_diffrn_reflns_limit_h_min       -9
_diffrn_reflns_limit_k_max       9
_diffrn_reflns_limit_k_min       -9
_diffrn_reflns_limit_l_max       6
_diffrn_reflns_limit_l_min       -6
_diffrn_reflns_number            940
_diffrn_reflns_point_group_measured_fraction_full 0.663
_diffrn_reflns_point_group_measured_fraction_max 0.657
_diffrn_reflns_theta_full        10.040
_diffrn_reflns_theta_max         10.458
_diffrn_reflns_theta_min         1.701
_diffrn_source                   synchrotron
_diffrn_source_type              'PETRA III, Beamline P02.2'
_exptl_absorpt_coefficient_mu    0.221
_exptl_crystal_colour            colorless
_exptl_crystal_density_diffrn    4.152
_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         1.185
_refine_diff_density_min         -0.983
_refine_diff_density_rms         0.296
_refine_ls_extinction_method     none
_refine_ls_goodness_of_fit_ref   1.175
_refine_ls_hydrogen_treatment    undef
_refine_ls_matrix_type           full
_refine_ls_number_parameters     68
_refine_ls_number_reflns         524
_refine_ls_number_restraints     0
_refine_ls_restrained_S_all      1.175
_refine_ls_R_factor_all          0.1252
_refine_ls_R_factor_gt           0.0979
_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^)+(0.1924P)^2^+3.6413P] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.2941
_refine_ls_wR_factor_ref         0.3095
_reflns_Friedel_coverage         0.000
_reflns_number_gt                408
_reflns_number_total             524
_reflns_threshold_expression     'I > 2\s(I)'
_cod_data_source_file            lt5006.cif
_cod_data_source_block           danburite-IV_32.3GPa
_cod_database_code               1546778
_shelx_shelxl_version_number     2014/7
_shelx_res_checksum              48898
_shelx_hkl_checksum              23081