data_p0 _publ_requested_journal Am.Miner. _publ_section_title 'High-pressure phase transition of a natural pigeonite' _publ_contact_author_name 'MATTEO ALVARO' _publ_contact_author_address ; 'Dipartimento di Scienze della Terra, Universit\`a di Pavia, Via Ferrata 1, I-27100 Pavia (Italy)' ; loop_ _publ_author_name _publ_author_address 'ALVARO, MATTEO' ;'Dipartimento di Scienze della Terra, Universit\`a di Pavia, Via Ferrata 1, I-27100 Pavia (Italy)' ; 'Nestola, Fabrizio' ;'Dipartimento di Geoscienze, Universit\`a di Padova, Via Giotto 1, I-35137 Padova (Italy)' ; 'BOFFA BALLARAN, TIZIANA' ;'Bayerisches Geoinstitut, Universit\"at Bayreuth, Universit\"atstrasse 37, D-95440 Bayreuth (Germany)' ; 'C\'AMARA, FERNANDO' ;'C.N.R. - Istituto di Geoscienze e Georisorse - Unit\`a di Pavia, Via Ferrata 1, I-27100 Pavia (Italy)' ; 'DOMENEGHETTI, CHIARA' ;'Dipartimento di Scienze della Terra, Universit\`a di Pavia, Via Ferrata 1, I-27100 Pavia (Italy)' ; 'TAZZOLI, VITTORIO' ;'Dipartimento di Scienze della Terra, Universit\`a di Pavia, Via Ferrata 1, I-27100 Pavia (Italy)' ; _audit_creation_method SHELXL-97 _chemical_name_systematic Pigeonite _chemical_name_common ? _chemical_melting_point ? _chemical_formula_sum 'Ca0.48 Fe4 Mg3.48 O24 Si8' _chemical_formula_weight 935.96 loop_ _atom_type_symbol _atom_type_description _atom_type_scat_dispersion_real _atom_type_scat_dispersion_imag _atom_type_scat_source O O 0.0106 0.0060 'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4' O O-- 0.0080 0.0060 'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4' Si Si 0.0817 0.0704 'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4' Si SiP4 0.0720 0.0710 'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4' Mg MgP2 0.0420 0.0360 'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4' Fe FeP2 0.3010 0.8450 'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4' Ca Ca+2 0.2030 0.3060 'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4' Si Si+2 0.0720 0.0710 'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4' _symmetry_cell_setting monoclinic _symmetry_space_group_name_H-M 'P 21/c' _symmetry_int_tables_number 14 loop_ _symmetry_equiv_pos_as_xyz 'x, y, z' '-x, y+1/2, -z+1/2' '-x, -y, -z' 'x, -y-1/2, z-1/2' _cell_length_a 9.749(9) _cell_length_b 8.937(8) _cell_length_c 5.246(5) _cell_angle_alpha 90.00 _cell_angle_beta 108.49(9) _cell_angle_gamma 90.00 _cell_volume 433.5(7) _cell_formula_units_Z 4 _cell_measurement_temperature 293(2) _cell_measurement_reflns_used ? _cell_measurement_theta_min ? _cell_measurement_theta_max ? _exptl_crystal_description Irregular _exptl_crystal_colour Green _exptl_crystal_size_max 0.120 _exptl_crystal_size_mid 0.110 _exptl_crystal_size_min 0.100 _exptl_crystal_density_meas ? _exptl_crystal_density_diffrn 3.585 _exptl_crystal_density_method 'not measured' _exptl_crystal_F_000 460.0 _exptl_absorpt_coefficient_mu 4.248 _exptl_absorpt_correction_type numerical _exptl_absorpt_correction_T_min ? _exptl_absorpt_correction_T_max ? _exptl_absorpt_process_details ABSORB _exptl_special_details ; Angel, R.J. (2004) Absorption corrections for diamond-anvil pressure cells implemented in the software package -- Absorb 6.0. Journal of Applied Crystallography, 37, 486-492. ; _diffrn_ambient_temperature 293(2) _diffrn_radiation_probe x-ray _diffrn_radiation_type MoK\a _diffrn_radiation_wavelength 0.71070 _diffrn_source 'fine-focus sealed tube' _diffrn_radiation_monochromator graphite _diffrn_measurement_device_type ? _diffrn_measurement_method ? _diffrn_detector_area_resol_mean ? _diffrn_standards_number ? _diffrn_standards_interval_count ? _diffrn_standards_interval_time ? _diffrn_standards_decay_% ? _diffrn_reflns_number 983 _diffrn_reflns_av_R_equivalents 0.0000 _diffrn_reflns_av_sigmaI/netI 0.0453 _diffrn_reflns_limit_h_min -11 _diffrn_reflns_limit_h_max 10 _diffrn_reflns_limit_k_min 0 _diffrn_reflns_limit_k_max 11 _diffrn_reflns_limit_l_min 0 _diffrn_reflns_limit_l_max 7 _diffrn_reflns_theta_min 3.17 _diffrn_reflns_theta_max 30.01 _reflns_number_total 983 _reflns_number_gt 662 _reflns_threshold_expression >2sigma(I) _computing_data_collection ? _computing_cell_refinement ? _computing_data_reduction ? _computing_structure_solution ? _computing_structure_refinement 'SHELXL-97 (Sheldrick, 1997)' _computing_molecular_graphics ? _computing_publication_material ? _refine_special_details ; Refinement of F^2^ against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F^2^, conventional R-factors R are based on F, with F set to zero for negative F^2^. The threshold expression of F^2^ > 2sigma(F^2^) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F^2^ are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. ; _refine_ls_structure_factor_coef Fsqd _refine_ls_matrix_type full _refine_ls_weighting_scheme calc _refine_ls_weighting_details 'calc w=1/[\s^2^(Fo^2^)+(0.0846P)^2^+0.5422P] where P=(Fo^2^+2Fc^2^)/3' _atom_sites_solution_primary direct _atom_sites_solution_secondary difmap _refine_ls_extinction_method none _refine_ls_extinction_coef ? _refine_ls_number_reflns 983 _refine_ls_number_parameters 62 _refine_ls_number_restraints 7 _refine_ls_R_factor_all 0.1144 _refine_ls_R_factor_gt 0.0755 _refine_ls_wR_factor_ref 0.2141 _refine_ls_wR_factor_gt 0.1825 _refine_ls_goodness_of_fit_ref 1.114 _refine_ls_restrained_S_all 1.130 _refine_ls_shift/su_max 0.000 _refine_ls_shift/su_mean 0.000 loop_ _atom_site_label _atom_site_type_symbol _atom_site_fract_x _atom_site_fract_y _atom_site_fract_z _atom_site_U_iso_or_equiv _atom_site_adp_type _atom_site_occupancy _atom_site_symmetry_multiplicity _atom_site_calc_flag _atom_site_refinement_flags _atom_site_disorder_assembly _atom_site_disorder_group O1A O 0.8668(11) 0.3374(7) 0.1683(12) 0.0082(14) Uiso 1 1 d . . . O1B O 0.3734(11) 0.8373(7) 0.1332(13) 0.0087(14) Uiso 1 1 d . . . O2A O 0.1183(11) 0.4971(8) 0.3300(13) 0.0119(15) Uiso 1 1 d . . . O2B O 0.6332(12) 0.9886(8) 0.3721(14) 0.0165(16) Uiso 1 1 d . . . O3A O 0.1004(13) 0.2599(8) 0.5718(15) 0.0202(17) Uiso 1 1 d . . . O3B O 0.6067(12) 0.7130(8) 0.4840(14) 0.0159(17) Uiso 1 1 d . . . SiA Si+2 0.0428(5) 0.3400(3) 0.2745(5) 0.0086(6) Uiso 1 1 d . . . SiB Si+2 0.5482(5) 0.8383(3) 0.2384(5) 0.0089(6) Uiso 1 1 d . . . M1A MgP2 0.2505(4) 0.6546(2) 0.2322(5) 0.0104(9) Uani 0.75 1 d P . . M1B FeP2 0.2505(4) 0.6546(2) 0.2322(5) 0.0104(9) Uani 0.25 1 d P . . M2A MgP2 0.2558(5) 0.0177(4) 0.2294(6) 0.0135(7) Uani 0.12 1 d PDU . . M2B FeP2 0.2558(5) 0.0177(4) 0.2294(6) 0.0135(7) Uani 0.75 1 d P . . M21 Ca+2 0.246(7) 0.039(5) 0.264(9) 0.030 Uiso 0.12 1 d PDU . . loop_ _atom_site_aniso_label _atom_site_aniso_U_11 _atom_site_aniso_U_22 _atom_site_aniso_U_33 _atom_site_aniso_U_23 _atom_site_aniso_U_13 _atom_site_aniso_U_12 M1A 0.014(3) 0.0075(13) 0.0104(11) 0.0008(9) 0.0045(14) 0.0002(13) M1B 0.014(3) 0.0075(13) 0.0104(11) 0.0008(9) 0.0045(14) 0.0002(13) M2A 0.015(2) 0.0144(14) 0.0102(12) 0.0017(8) 0.0028(11) 0.0018(11) M2B 0.015(2) 0.0144(14) 0.0102(12) 0.0017(8) 0.0028(11) 0.0018(11) _geom_special_details ; All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. ; loop_ _geom_bond_atom_site_label_1 _geom_bond_atom_site_label_2 _geom_bond_distance _geom_bond_site_symmetry_2 _geom_bond_publ_flag O1A SiA 1.627(10) 1_655 ? O1A M1A 2.050(8) 3_665 ? O1A M1A 2.151(8) 2_645 ? O1A M2A 2.172(9) 2_655 ? O1A M21 2.20(6) 2_655 ? O1B SiB 1.617(10) . ? O1B M1A 2.066(8) 4_575 ? O1B M2A 2.129(8) 1_565 ? O1B M1A 2.183(8) . ? O2A SiA 1.569(8) . ? O2A M1A 2.080(9) . ? O2A M2A 2.103(9) 4_566 ? O2A M21 2.25(5) 4_566 ? O2B SiB 1.617(9) . ? O2B M21 1.91(6) 3_666 ? O2B M2A 2.027(9) 3_666 ? O2B M1A 2.044(9) 2_655 ? O3A SiA 1.620(8) 4_566 ? O3A SiA 1.645(8) . ? O3A M2A 2.477(10) 4_566 ? O3A O3A 2.629(3) 4_565 ? O3A O3A 2.629(3) 4_566 ? O3A M2A 3.454(9) . ? O3B SiB 1.666(8) . ? O3B SiB 1.673(8) 4_576 ? O3B M2A 2.655(9) 2_655 ? O3B O3B 2.705(4) 4_576 ? O3B O3B 2.705(4) 4_575 ? O3B M2A 2.928(9) 3_666 ? SiA O3A 1.620(8) 4_565 ? SiA O1A 1.627(10) 1_455 ? SiB O3B 1.673(8) 4_575 ? M1A O2B 2.044(9) 2_645 ? M1A O1A 2.050(8) 3_665 ? M1A O1B 2.066(8) 4_576 ? M1A O1A 2.151(8) 2_655 ? M1A M21 3.00(5) 4_565 ? M1A M2A 3.015(4) 4_566 ? M1A M2A 3.068(5) 4_565 ? M2A M21 0.300(19) . ? M2A O2B 2.027(9) 3_666 ? M2A O2A 2.103(9) 4_565 ? M2A O1B 2.129(8) 1_545 ? M2A O1A 2.172(9) 2_645 ? M2A O3A 2.477(10) 4_565 ? M2A O3B 2.655(9) 2_645 ? M2A SiA 2.912(6) 4_565 ? M2A O3B 2.928(9) 3_666 ? M21 O2B 1.91(6) 3_666 ? M21 O1A 2.20(6) 2_645 ? M21 O2A 2.25(5) 4_565 ? M21 M1A 3.00(5) 4_566 ? loop_ _geom_angle_atom_site_label_1 _geom_angle_atom_site_label_2 _geom_angle_atom_site_label_3 _geom_angle _geom_angle_site_symmetry_1 _geom_angle_site_symmetry_3 _geom_angle_publ_flag SiA O1A M1A 122.4(4) 1_655 3_665 ? SiA O1A M1A 120.8(4) 1_655 2_645 ? M1A O1A M1A 96.2(4) 3_665 2_645 ? SiA O1A M2A 120.5(4) 1_655 2_655 ? M1A O1A M2A 93.2(4) 3_665 2_655 ? M1A O1A M2A 97.3(4) 2_645 2_655 ? SiA O1A M21 117.4(16) 1_655 2_655 ? M1A O1A M21 89.5(15) 3_665 2_655 ? M1A O1A M21 104.6(9) 2_645 2_655 ? SiB O1B M1A 123.8(4) . 4_575 ? SiB O1B M2A 120.2(4) . 1_565 ? M1A O1B M2A 91.9(4) 4_575 1_565 ? SiB O1B M1A 121.5(4) . . ? M1A O1B M1A 94.8(4) 4_575 . ? M2A O1B M1A 97.6(4) 1_565 . ? SiA O2A M1A 148.3(4) . . ? SiA O2A M2A 104.0(4) . 4_566 ? M1A O2A M2A 92.2(4) . 4_566 ? SiA O2A M21 97.8(10) . 4_566 ? M1A O2A M21 99.2(10) . 4_566 ? SiB O2B M21 113.0(16) . 3_666 ? SiB O2B M2A 117.2(4) . 3_666 ? SiB O2B M1A 137.6(4) . 2_655 ? M21 O2B M1A 98.4(19) 3_666 2_655 ? M2A O2B M1A 97.8(4) 3_666 2_655 ? SiA O3A SiA 141.0(8) 4_566 . ? SiA O3A M2A 121.7(4) 4_566 4_566 ? SiA O3A M2A 87.5(4) . 4_566 ? SiA O3A O3A 136.7(5) 4_566 4_565 ? M2A O3A O3A 101.2(3) 4_566 4_565 ? SiA O3A O3A 150.1(5) . 4_566 ? M2A O3A O3A 85.1(3) 4_566 4_566 ? O3A O3A O3A 172.3(6) 4_565 4_566 ? SiA O3A M2A 107.2(3) 4_566 . ? SiA O3A M2A 81.6(3) . . ? M2A O3A M2A 110.7(4) 4_566 . ? O3A O3A M2A 45.6(2) 4_565 . ? O3A O3A M2A 128.0(4) 4_566 . ? SiB O3B SiB 133.0(7) . 4_576 ? SiB O3B M2A 102.2(3) . 2_655 ? SiB O3B M2A 120.1(4) 4_576 2_655 ? SiB O3B O3B 118.7(5) . 4_576 ? M2A O3B O3B 136.5(3) 2_655 4_576 ? SiB O3B O3B 161.0(4) 4_576 4_575 ? M2A O3B O3B 66.2(2) 2_655 4_575 ? O3B O3B O3B 151.7(6) 4_576 4_575 ? SiB O3B M2A 80.4(3) . 3_666 ? SiB O3B M2A 91.8(3) 4_576 3_666 ? M2A O3B M2A 123.1(4) 2_655 3_666 ? O3B O3B M2A 56.1(3) 4_576 3_666 ? O3B O3B M2A 99.0(4) 4_575 3_666 ? O2A SiA O3A 112.0(5) . 4_565 ? O2A SiA O1A 117.3(4) . 1_455 ? O3A SiA O1A 108.3(5) 4_565 1_455 ? O2A SiA O3A 102.4(5) . . ? O3A SiA O3A 107.3(4) 4_565 . ? O1A SiA O3A 108.9(5) 1_455 . ? O2B SiB O1B 119.5(5) . . ? O2B SiB O3B 102.8(5) . . ? O1B SiB O3B 109.0(4) . . ? O2B SiB O3B 108.4(5) . 4_575 ? O1B SiB O3B 108.4(5) . 4_575 ? O3B SiB O3B 108.3(4) . 4_575 ? O2B M1A O1A 85.9(3) 2_645 3_665 ? O2B M1A O1B 96.1(3) 2_645 4_576 ? O1A M1A O1B 175.7(3) 3_665 4_576 ? O2B M1A O2A 90.8(4) 2_645 . ? O1A M1A O2A 95.1(3) 3_665 . ? O1B M1A O2A 88.7(3) 4_576 . ? O2B M1A O1A 177.1(3) 2_645 2_655 ? O1A M1A O1A 93.2(3) 3_665 2_655 ? O1B M1A O1A 84.7(3) 4_576 2_655 ? O2A M1A O1A 92.0(3) . 2_655 ? O2B M1A O1B 95.0(3) 2_645 . ? O1A M1A O1B 84.3(3) 3_665 . ? O1B M1A O1B 91.8(4) 4_576 . ? O2A M1A O1B 174.1(3) . . ? O1A M1A O1B 82.2(3) 2_655 . ? O2B M1A M21 39.2(13) 2_645 4_565 ? O1A M1A M21 47.3(12) 3_665 4_565 ? O1B M1A M21 135.1(12) 4_576 4_565 ? O2A M1A M21 87.8(6) . 4_565 ? O1A M1A M21 140.2(13) 2_655 4_565 ? O1B M1A M21 96.0(5) . 4_565 ? O2B M1A M2A 90.1(2) 2_645 4_566 ? O1A M1A M2A 139.1(3) 3_665 4_566 ? O1B M1A M2A 44.9(2) 4_576 4_566 ? O2A M1A M2A 44.2(2) . 4_566 ? O1A M1A M2A 92.4(2) 2_655 4_566 ? O1B M1A M2A 136.7(3) . 4_566 ? M21 M1A M2A 113.9(5) 4_565 4_566 ? O2B M1A M2A 40.9(2) 2_645 4_565 ? O1A M1A M2A 45.0(2) 3_665 4_565 ? O1B M1A M2A 136.9(3) 4_576 4_565 ? O2A M1A M2A 93.1(2) . 4_565 ? O1A M1A M2A 138.1(2) 2_655 4_565 ? O1B M1A M2A 90.61(18) . 4_565 ? M21 M1A M2A 5.5(4) 4_565 4_565 ? M2A M1A M2A 119.16(15) 4_566 4_565 ? M21 M2A O2B 64(10) . 3_666 ? M21 M2A O2A 115(10) . 4_565 ? O2B M2A O2A 171.4(4) 3_666 4_565 ? M21 M2A O1B 158(10) . 1_545 ? O2B M2A O1B 94.1(4) 3_666 1_545 ? O2A M2A O1B 86.4(3) 4_565 1_545 ? M21 M2A O1A 92(10) . 2_645 ? O2B M2A O1A 83.1(3) 3_666 2_645 ? O2A M2A O1A 88.4(3) 4_565 2_645 ? O1B M2A O1A 82.9(3) 1_545 2_645 ? M21 M2A O3A 54(10) . 4_565 ? O2B M2A O3A 115.9(3) 3_666 4_565 ? O2A M2A O3A 65.7(3) 4_565 4_565 ? O1B M2A O3A 147.8(3) 1_545 4_565 ? O1A M2A O3A 110.6(4) 2_645 4_565 ? M21 M2A O3B 97(10) . 2_645 ? O2B M2A O3B 106.1(4) 3_666 2_645 ? O2A M2A O3B 82.5(3) 4_565 2_645 ? O1B M2A O3B 90.9(3) 1_545 2_645 ? O1A M2A O3B 169.3(2) 2_645 2_645 ? O3A M2A O3B 70.7(3) 4_565 2_645 ? M21 M2A SiA 86(10) . 4_565 ? O2B M2A SiA 150.0(3) 3_666 4_565 ? O2A M2A SiA 31.5(2) 4_565 4_565 ? O1B M2A SiA 115.7(2) 1_545 4_565 ? O1A M2A SiA 102.8(3) 2_645 4_565 ? O3A M2A SiA 34.34(19) 4_565 4_565 ? O3B M2A SiA 72.0(3) 2_645 4_565 ? M21 M2A O3B 48(10) . 3_666 ? O2B M2A O3B 59.0(3) 3_666 3_666 ? O2A M2A O3B 127.3(3) 4_565 3_666 ? O1B M2A O3B 123.4(4) 1_545 3_666 ? O1A M2A O3B 132.9(2) 2_645 3_666 ? O3A M2A O3B 69.1(3) 4_565 3_666 ? O3B M2A O3B 57.71(16) 2_645 3_666 ? SiA M2A O3B 98.8(2) 4_565 3_666 ? M2A M21 O2B 108(10) . 3_666 ? M2A M21 O1A 80(10) . 2_645 ? O2B M21 O1A 85(2) 3_666 2_645 ? M2A M21 O2A 58(10) . 4_565 ? O2B M21 O2A 164(2) 3_666 4_565 ? O1A M21 O2A 84(2) 2_645 4_565 ? M2A M21 M1A 101(10) . 4_566 ? O2B M21 M1A 42.4(11) 3_666 4_566 ? O1A M21 M1A 43.2(10) 2_645 4_566 ? O2A M21 M1A 127(2) 4_565 4_566 ? _diffrn_measured_fraction_theta_max 0.610 _diffrn_reflns_theta_full 30.01 _diffrn_measured_fraction_theta_full 0.610 _refine_diff_density_max 1.760 _refine_diff_density_min -1.856 _refine_diff_density_rms 0.505 _diffrn_ambient_pressure 100 _chemical_formula_moiety 'Ca0.48 Fe4 Mg3.48 O24 Si8'