New phosphate langbeinites, K~2~<i>M</i>Ti(PO~4~)~3~ (<i>M</i> = Er, Yb or Y), and an alternative description of the langbeinite framework
Norberg, Stefan T.; Acta Crystallographica Section B 58 (2002) 743–749; doi:10.1107/S0108768102013782

data_2103456
_publ_section_title
;
 New phosphate langbeinites, K~2~<i>M</i>Ti(PO~4~)~3~ (<i>M</i> = Er,
 Yb or Y), and an alternative description of the langbeinite framework
;
_journal_issue                   5
_journal_name_full               'Acta Crystallographica Section B'
_journal_page_first              743
_journal_page_last               749
_journal_paper_doi               10.1107/S0108768102013782
_journal_volume                  58
_journal_year                    2002
_chemical_formula_moiety         'K2 Er Ti P3 O12'
_chemical_formula_structural     'K2 Er Ti (P O4)3'
_chemical_formula_sum            'Er K2 O12 P3 Ti'
_chemical_formula_weight         578.25
_space_group_IT_number           198
_symmetry_cell_setting           cubic
_symmetry_space_group_name_Hall  'P 2ac 2ab 3'
_symmetry_space_group_name_H-M   'P 21 3'
_cell_angle_alpha                90
_cell_angle_beta                 90
_cell_angle_gamma                90
_cell_formula_units_Z            4
_cell_length_a                   10.1053(2)
_cell_length_b                   10.1053(2)
_cell_length_c                   10.1053(2)
_cell_measurement_reflns_used    20
_cell_measurement_temperature    293(2)
_cell_measurement_theta_max      29.76
_cell_measurement_theta_min      26.62
_cell_volume                     1031.92(4)
_computing_cell_refinement       'CAD-4 Software (Enraf-Nonius, 1989)'
_computing_data_collection       'CAD-4 Software (Enraf-Nonius, 1989)'
_computing_data_reduction
'Xtal3.71 (Hall et al., 2000) programs: DIFDAT; SORTRF; ADDREF; ABSORB'
_computing_publication_material
'Xtal3.71 (Hall et al., 2000) programs: BONDLA; ATABLE; CIFIO'
_computing_structure_refinement
'Xtal3.71 (Hall et al., 2000) program: CRYLSQ'
_computing_structure_solution    'SHELXS97 (Sheldrick, 1997)'
_diffrn_ambient_temperature      293(2)
_diffrn_measurement_device_type  'Enraf-Nonius CAD-4 diffractometer'
_diffrn_measurement_method       \w-2\q
_diffrn_radiation_monochromator  graphite
_diffrn_radiation_source         'Fine-focus sealed tube'
_diffrn_radiation_type           'Mo K\a'
_diffrn_radiation_wavelength     .71073
_diffrn_reflns_av_R_equivalents  0.048
_diffrn_reflns_limit_h_max       0
_diffrn_reflns_limit_h_min       -14
_diffrn_reflns_limit_k_max       0
_diffrn_reflns_limit_k_min       -14
_diffrn_reflns_limit_l_max       14
_diffrn_reflns_limit_l_min       -14
_diffrn_reflns_number            3285
_diffrn_reflns_reduction_process 'perpendicular monochr Lp'
_diffrn_reflns_theta_max         29.91
_diffrn_reflns_theta_min         3.49
_diffrn_standards_decay_%        0
_diffrn_standards_interval_time  120
_diffrn_standards_number         3
_exptl_absorpt_coefficient_mu    10.187
_exptl_absorpt_correction_T_max  .650
_exptl_absorpt_correction_T_min  .567
_exptl_absorpt_correction_type   analytical
_exptl_absorpt_process_details   '(Alcock, 1974)'
_exptl_crystal_colour            colourless
_exptl_crystal_density_diffrn    3.722
_exptl_crystal_density_meas      ?
_exptl_crystal_description       tetrahedron
_exptl_crystal_F_000             1076
_exptl_crystal_size_max          0.06
_exptl_crystal_size_mid          0.06
_exptl_crystal_size_min          0.05
_refine_diff_density_max         .60
_refine_diff_density_min         -.76
_refine_ls_abs_structure_details 'Flack (1983) parameter refined'
_refine_ls_abs_structure_Flack   .04(3)
_refine_ls_extinction_coef       '90(22) \\times 10^2^'
_refine_ls_extinction_expression
'Zachariasen, 1967; Larson (1970), Eq22 p292 "Cryst. Comp." Munksgaard 1970'
_refine_ls_extinction_method     'Isotropic Gaussian'
_refine_ls_goodness_of_fit_all   1.060
_refine_ls_goodness_of_fit_ref   1.060
_refine_ls_hydrogen_treatment    none
_refine_ls_matrix_type           full
_refine_ls_number_constraints    9
_refine_ls_number_parameters     61
_refine_ls_number_reflns         1008
_refine_ls_number_restraints     0
_refine_ls_R_factor_all          .025
_refine_ls_R_factor_gt           .023
_refine_ls_shift/su_max          .00018
_refine_ls_shift/su_mean         .000017
_refine_ls_structure_factor_coef Fsqd
_refine_ls_weighting_details     'w = 1/[\s^2^(Fsqd) + 0.008(Fsqd)^2^]'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_all         .077
_refine_ls_wR_factor_gt          .074
_refine_ls_wR_factor_ref         .077
_reflns_number_gt                967
_reflns_number_total             1008
_reflns_threshold_expression     'Fsqd > 2\s(Fsqd)'
_cod_data_source_file            os0095.cif
_cod_data_source_block           KErTP
_cod_database_code               2103456
_cod_database_fobs_code          2103456