A Transition from Localized to Strongly Correlated Electron Behavior and Mixed Valence Driven by Physical or Chemical Pressure in ACo2As2 (A = Eu and Ca).
Tan, Xiaoyan; Fabbris, Gilberto; Haskel, Daniel; Yaroslavtsev, Alexander A.; Cao, Huibo; Thompson, Corey M.; Kovnir, Kirill; Menushenkov, Alexey P.; Chernikov, Roman V.; Garlea, V. Ovidiu; Shatruk, Michael; Journal of the American Chemical Society 138 (2016) 2724–2731; doi:10.1021/jacs.5b12659

data_4124927
_publ_section_title
;
 A Transition from Localized to Strongly Correlated Electron Behavior and
 Mixed Valence Driven by Physical or Chemical Pressure in ACo2As2 (A = Eu
 and Ca).
;
_journal_issue                   8
_journal_name_full               'Journal of the American Chemical Society'
_journal_page_first              2724
_journal_page_last               2731
_journal_paper_doi               10.1021/jacs.5b12659
_journal_volume                  138
_journal_year                    2016
_chemical_formula_sum            'As2 Co2 Eu'
_chemical_formula_weight         419.43
_chemical_name_systematic        2014/7
_space_group_crystal_system      tetragonal
_space_group_IT_number           139
_space_group_name_Hall           '-I 4 2'
_space_group_name_H-M_alt        'I 4/m m m'
_symmetry_space_group_name_Hall  '-I 4 2'
_symmetry_space_group_name_H-M   'I 4/m m m'
_audit_creation_method           SHELXL-2014
_cell_angle_alpha                90
_cell_angle_beta                 90
_cell_angle_gamma                90
_cell_formula_units_Z            2
_cell_length_a                   3.9290(13)
_cell_length_b                   3.9290(13)
_cell_length_c                   11.512(4)
_cell_measurement_reflns_used    1584
_cell_measurement_temperature    293(2)
_cell_measurement_theta_max      47.57
_cell_measurement_theta_min      3.54
_cell_volume                     177.71(10)
_computing_cell_refinement       'SMART V5.625 (Bruker, 2000)'
_computing_data_collection       'SMART V5.625 (Bruker, 2000)'
_computing_data_reduction        'SAINT V6.32 (Bruker, 2001)'
_computing_molecular_graphics    'CrystalMaker V9.2.2 (2015)'
_computing_publication_material  'SHELXL-97 (Sheldrick, 1997)'
_computing_structure_refinement  'SHELXL-2014 (Sheldrick, 2014)'
_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 APEX II CCD area-detector'
_diffrn_measurement_method       'profile data from \w scans'
_diffrn_radiation_type           MoK\a
_diffrn_radiation_wavelength     0.71073
_diffrn_reflns_av_R_equivalents  0.0256
_diffrn_reflns_av_unetI/netI     0.0150
_diffrn_reflns_laue_measured_fraction_full 1.000
_diffrn_reflns_laue_measured_fraction_max 1.000
_diffrn_reflns_limit_h_max       6
_diffrn_reflns_limit_h_min       -6
_diffrn_reflns_limit_k_max       6
_diffrn_reflns_limit_k_min       -6
_diffrn_reflns_limit_l_max       18
_diffrn_reflns_limit_l_min       -18
_diffrn_reflns_number            1302
_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         36.295
_diffrn_reflns_theta_min         3.540
_diffrn_source                   'sealed tube'
_exptl_absorpt_coefficient_mu    44.861
_exptl_absorpt_correction_T_max  0.7494
_exptl_absorpt_correction_T_min  0.4130
_exptl_absorpt_correction_type   empirical
_exptl_absorpt_process_details   'SADABS v2.03 (Bruker, 2003)'
_exptl_crystal_colour            black
_exptl_crystal_density_diffrn    7.843
_exptl_crystal_description       plate
_exptl_crystal_F_000             366
_exptl_crystal_size_max          0.05
_exptl_crystal_size_mid          0.05
_exptl_crystal_size_min          0.02
_refine_diff_density_max         1.312
_refine_diff_density_min         -2.722
_refine_diff_density_rms         0.294
_refine_ls_extinction_coef       0.0188(18)
_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   1.259
_refine_ls_hydrogen_treatment    undef
_refine_ls_matrix_type           full
_refine_ls_number_parameters     10
_refine_ls_number_reflns         160
_refine_ls_number_restraints     0
_refine_ls_restrained_S_all      1.259
_refine_ls_R_factor_all          0.0191
_refine_ls_R_factor_gt           0.0188
_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^)+(0.0285P)^2^+0.4902P] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.0494
_refine_ls_wR_factor_ref         0.0496
_reflns_Friedel_coverage         0.000
_reflns_number_gt                158
_reflns_number_total             160
_reflns_threshold_expression     'I > 2\s(I)'
_cod_data_source_file            ja5b12659_si_002.cif
_cod_data_source_block           shelx
_cod_depositor_comments
'Adding full bibliography for 4124924--4124927.cif.'
_cod_original_cell_volume        177.70(14)
_cod_database_code               4124927
_shelxl_version_number           2014-3
_shelx_res_checksum              15718
_shelx_hkl_checksum              36592