Crystal structure across the β to α phase transition in thermoelectric Cu<sub>2-<i>x</i></sub> Se.
Eikeland, Espen; Blichfeld, Anders B.; Borup, Kasper A.; Zhao, Kunpeng; Overgaard, Jacob; Shi, Xun; Chen, Lidong; Iversen, Bo B.; IUCrJ 4 (2017) 476–485; doi:10.1107/S2052252517005553

data_1556748
_publ_section_title
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 Crystal structure across the \b to \a phase transition in thermoelectric
 Cu<sub>2-<i>x</i></sub> Se.
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_journal_coeditor_code           LC5071SUP1
_journal_issue                   'Pt 4'
_journal_name_full               IUCrJ
_journal_page_first              476
_journal_page_last               485
_journal_paper_doi               10.1107/S2052252517005553
_journal_volume                  4
_journal_year                    2017
_chemical_formula_moiety         '0.33(Cu5.85 Se3)'
_chemical_formula_sum            'Cu1.95 Se'
_chemical_formula_weight         202.76
_chemical_name_systematic        alpha-Cu2-xSe
_space_group_crystal_system      trigonal
_space_group_IT_number           166
_space_group_name_Hall           '-R 3 2"'
_space_group_name_H-M_alt        'R -3 m :H'
_audit_creation_date             2017-01-24
_audit_creation_method
;
Olex2 1.2
(compiled 2017.01.04 svn.r3372 for OlexSys, GUI svn.r5292)
;
_cell_angle_alpha                90
_cell_angle_beta                 90
_cell_angle_gamma                120
_cell_formula_units_Z            6
_cell_length_a                   4.1227(8)
_cell_length_b                   4.1227(8)
_cell_length_c                   20.449(6)
_cell_measurement_reflns_used    574
_cell_measurement_temperature    295
_cell_measurement_theta_max      27.7130
_cell_measurement_theta_min      2.9500
_cell_volume                     301.00(12)
_computing_cell_refinement       'CrysAlisPro 1.171.38.41 (Rigaku OD, 2015)'
_computing_data_collection       'CrysAlisPro 1.171.38.41 (Rigaku OD, 2015)'
_computing_data_reduction        'CrysAlisPro 1.171.38.41 (Rigaku OD, 2015)'
_computing_molecular_graphics    'Olex2 (Dolomanov et al., 2009)'
_computing_publication_material  'Olex2 (Dolomanov et al., 2009)'
_computing_structure_refinement  'ShelXL (Sheldrick, 2015)'
_computing_structure_solution    'ShelXT (Sheldrick, 2015)'
_diffrn_ambient_temperature      295.0
_diffrn_detector_area_resol_mean 10.3590
_diffrn_detector_type            Atlas
_diffrn_measured_fraction_theta_full 1.000
_diffrn_measured_fraction_theta_max 1.000
_diffrn_measurement_details
;
List of Runs (angles in degrees, time in seconds):

  # Type    Start    End  Width  t~exp~   \w     \q     \k     \f   Frames
--------------------------------------------------------------------------
  1  \w    -25.00 119.00   1.00   60.00    --   18.69  77.00   0.00  144
  2  \w    -25.00 119.00   1.00   60.00    --   18.69  77.00-120.00  144
  3  \w    -16.00  27.00   1.00   60.00    --   18.69  77.00-180.00   43
  4  \w    -59.00  47.00   1.00   60.00    --  -19.62  77.00 120.00  106
;
_diffrn_measurement_device       'four-circle diffractometer'
_diffrn_measurement_device_type  'SuperNova, Single source at offset, Atlas'
_diffrn_measurement_method       '\w scans'
_diffrn_radiation_type           MoK\a
_diffrn_radiation_wavelength     0.71073
_diffrn_reflns_av_R_equivalents  0.0752
_diffrn_reflns_av_unetI/netI     0.0302
_diffrn_reflns_Laue_measured_fraction_full 1.000
_diffrn_reflns_Laue_measured_fraction_max 1.000
_diffrn_reflns_limit_h_max       5
_diffrn_reflns_limit_h_min       -5
_diffrn_reflns_limit_k_max       3
_diffrn_reflns_limit_k_min       -5
_diffrn_reflns_limit_l_max       24
_diffrn_reflns_limit_l_min       -24
_diffrn_reflns_number            809
_diffrn_reflns_point_group_measured_fraction_full 1.000
_diffrn_reflns_point_group_measured_fraction_max 1.000
_diffrn_reflns_theta_full        25.242
_diffrn_reflns_theta_max         26.261
_diffrn_reflns_theta_min         2.988
_exptl_absorpt_coefficient_mu    38.277
_exptl_absorpt_correction_T_max  1.00000
_exptl_absorpt_correction_T_min  0.16926
_exptl_absorpt_correction_type   multi-scan
_exptl_absorpt_process_details
;
CrysAlisPro 1.171.38.41 (Rigaku Oxford Diffraction, 2015)
Empirical absorption correction using spherical harmonics,
 implemented in SCALE3 ABSPACK scaling algorithm.
;
_exptl_crystal_colour            'metallic grayish gray'
_exptl_crystal_colour_lustre     metallic
_exptl_crystal_colour_modifier   grayish
_exptl_crystal_colour_primary    gray
_exptl_crystal_density_diffrn    6.711
_exptl_crystal_description       irregular
_exptl_crystal_F_000             543
_exptl_crystal_size_max          0.0908
_exptl_crystal_size_mid          0.0493
_exptl_crystal_size_min          0.0167
_refine_diff_density_max         1.324
_refine_diff_density_min         -1.387
_refine_diff_density_rms         0.355
_refine_ls_extinction_method     none
_refine_ls_goodness_of_fit_ref   1.217
_refine_ls_hydrogen_treatment    undef
_refine_ls_matrix_type           full
_refine_ls_number_parameters     19
_refine_ls_number_reflns         102
_refine_ls_number_restraints     1
_refine_ls_restrained_S_all      1.210
_refine_ls_R_factor_all          0.0605
_refine_ls_R_factor_gt           0.0593
_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^)+(0.0987P)^2^+11.9258P] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.1562
_refine_ls_wR_factor_ref         0.1575
_reflns_Friedel_coverage         0.000
_reflns_number_gt                99
_reflns_number_total             102
_reflns_threshold_expression     'I > 2\s(I)'
_cod_data_source_file            lc5071.cif
_cod_data_source_block           Cu1p95Se_CVT1_295K
_cod_original_cell_volume        301.00(15)
_cod_original_sg_symbol_H-M      'R -3 m'
_cod_database_code               1556748
_shelx_shelxl_version_number     2014/7
_shelx_estimated_absorpt_t_max   0.567
_shelx_estimated_absorpt_t_min   0.129
_olex2_refinement_description
;
1. Others
 1*[Sof(Cu1A)]+1*[Sof(Cu1B)]+3*[Sof(Cu2)]=1.95 with esd of 0.01
 Fixed X: Se1(0.333301) Cu1B(0.6667) Cu1A(0.6667)
 Fixed Y: Se1(0.6667) Cu1B(0.333301) Cu1A(0.333301)
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