data_p12_totale _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 9.622(14) _cell_length_b 8.861(14) _cell_length_c 5.181(7) _cell_angle_alpha 90.00 _cell_angle_beta 107.92(13) _cell_angle_gamma 90.00 _cell_volume 420.3(11) _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 959 _diffrn_reflns_av_R_equivalents 0.0000 _diffrn_reflns_av_sigmaI/netI 0.0696 _diffrn_reflns_limit_h_min -12 _diffrn_reflns_limit_h_max 11 _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 3.20 _diffrn_reflns_theta_max 29.90 _reflns_number_total 959 _reflns_number_gt 649 _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^)+(0.0817P)^2^+0.0000P] 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 959 _refine_ls_number_parameters 62 _refine_ls_number_restraints 7 _refine_ls_R_factor_all 0.1349 _refine_ls_R_factor_gt 0.0766 _refine_ls_wR_factor_ref 0.1878 _refine_ls_wR_factor_gt 0.1579 _refine_ls_goodness_of_fit_ref 1.181 _refine_ls_restrained_S_all 1.207 _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(9) 0.3381(7) 0.1713(12) 0.0083(14) Uiso 1 1 d . . . O1B O 0.3741(9) 0.8374(7) 0.1307(12) 0.0083(13) Uiso 1 1 d . . . O2A O 0.1187(9) 0.5021(8) 0.3293(11) 0.0119(14) Uiso 1 1 d . . . O2B O 0.6276(10) 0.9878(7) 0.3708(12) 0.0131(14) Uiso 1 1 d . . . O3A O 0.1032(11) 0.2616(8) 0.5748(14) 0.0203(17) Uiso 1 1 d . . . O3B O 0.6065(10) 0.7055(8) 0.4714(13) 0.0134(16) Uiso 1 1 d . . . SiA Si+2 0.0418(4) 0.3417(3) 0.2740(5) 0.0086(6) Uiso 1 1 d . . . SiB Si+2 0.5497(4) 0.8380(3) 0.2334(5) 0.0079(6) Uiso 1 1 d . . . M1A MgP2 0.2505(4) 0.6563(3) 0.2284(4) 0.0100(6) Uani 0.75 1 d P . . M1B FeP2 0.2505(4) 0.6563(3) 0.2284(4) 0.0100(6) Uani 0.25 1 d P . . M2A MgP2 0.2562(5) 0.0218(3) 0.2234(4) 0.0111(6) Uani 0.12 1 d PDU . . M2B FeP2 0.2562(5) 0.0218(3) 0.2234(4) 0.0111(6) Uani 0.75 1 d P . . M21 Ca+2 0.251(7) 0.028(5) 0.277(6) 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 0.0122(19) 0.0079(13) 0.0103(10) 0.0006(9) 0.0038(11) 0.0039(12) M1B 0.0122(19) 0.0079(13) 0.0103(10) 0.0006(9) 0.0038(11) 0.0039(12) M2A 0.0104(15) 0.0151(11) 0.0065(10) 0.0042(9) 0.0006(11) 0.0021(9) M2B 0.0104(15) 0.0151(11) 0.0065(10) 0.0042(9) 0.0006(11) 0.0021(9) _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 1.603(9) 1_655 ? O1A M1A 2.032(8) 3_665 ? O1A M21 2.09(5) 2_655 ? O1A M1A 2.121(7) 2_645 ? O1A M2A 2.179(8) 2_655 ? O1B SiB 1.608(9) . ? O1B M1A 2.058(8) 4_575 ? O1B M2A 2.127(7) 1_565 ? O1B M1A 2.149(7) . ? O2A SiA 1.587(8) . ? O2A M1A 2.039(8) . ? O2A M2A 2.074(8) 4_566 ? O2B SiB 1.581(7) . ? O2B M21 1.84(4) 3_666 ? O2B M2A 2.057(8) 3_666 ? O2B M1A 2.059(8) 2_655 ? O3A SiA 1.621(8) 4_566 ? O3A SiA 1.647(8) . ? O3A M2A 2.397(9) 4_566 ? O3A O3A 2.599(4) 4_565 ? O3A O3A 2.599(4) 4_566 ? O3A M2A 3.413(8) . ? O3B SiB 1.657(7) 4_576 ? O3B SiB 1.668(7) . ? O3B M2A 2.497(8) 2_655 ? O3B O3B 2.708(5) 4_576 ? O3B O3B 2.708(5) 4_575 ? O3B M2A 2.966(8) 3_666 ? SiA O1A 1.603(9) 1_455 ? SiA O3A 1.621(8) 4_565 ? SiB O3B 1.657(7) 4_575 ? M1A O1A 2.032(8) 3_665 ? M1A O1B 2.058(8) 4_576 ? M1A O2B 2.059(8) 2_645 ? M1A O1A 2.121(7) 2_655 ? M1A M21 2.85(3) 4_565 ? M1A M2A 2.997(4) 4_566 ? M1A M2A 3.071(5) 4_565 ? M2A M21 0.303(18) . ? M2A O2B 2.057(8) 3_666 ? M2A O2A 2.074(8) 4_565 ? M2A O1B 2.127(7) 1_545 ? M2A O1A 2.179(8) 2_645 ? M2A O3A 2.397(9) 4_565 ? M2A O3B 2.497(8) 2_645 ? M2A SiA 2.861(6) 4_565 ? M2A O3B 2.966(8) 3_666 ? M21 O2B 1.84(4) 3_666 ? M21 O1A 2.09(5) 2_645 ? M21 M1A 2.85(3) 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 M21 119.9(16) 1_655 2_655 ? M1A O1A M21 87.5(11) 3_665 2_655 ? SiA O1A M1A 121.2(4) 1_655 2_645 ? M1A O1A M1A 95.6(3) 3_665 2_645 ? M21 O1A M1A 103.3(12) 2_655 2_645 ? SiA O1A M2A 119.9(4) 1_655 2_655 ? M1A O1A M2A 93.6(3) 3_665 2_655 ? M1A O1A M2A 97.8(3) 2_645 2_655 ? SiB O1B M1A 123.8(4) . 4_575 ? SiB O1B M2A 120.1(4) . 1_565 ? M1A O1B M2A 91.5(3) 4_575 1_565 ? SiB O1B M1A 121.7(4) . . ? M1A O1B M1A 94.0(3) 4_575 . ? M2A O1B M1A 98.5(3) 1_565 . ? SiA O2A M1A 147.7(4) . . ? SiA O2A M2A 101.9(3) . 4_566 ? M1A O2A M2A 93.6(4) . 4_566 ? SiB O2B M21 116.6(15) . 3_666 ? SiB O2B M2A 117.3(4) . 3_666 ? SiB O2B M1A 136.3(4) . 2_655 ? M21 O2B M1A 93.9(16) 3_666 2_655 ? M2A O2B M1A 96.5(4) 3_666 2_655 ? SiA O3A SiA 138.6(7) 4_566 . ? SiA O3A M2A 123.8(4) 4_566 4_566 ? SiA O3A M2A 88.0(3) . 4_566 ? SiA O3A O3A 134.6(5) 4_566 4_565 ? M2A O3A O3A 101.3(3) 4_566 4_565 ? SiA O3A O3A 150.1(4) . 4_566 ? M2A O3A O3A 86.1(3) 4_566 4_566 ? O3A O3A O3A 170.9(6) 4_565 4_566 ? SiA O3A M2A 106.8(3) 4_566 . ? SiA O3A M2A 81.5(3) . . ? M2A O3A M2A 110.3(3) 4_566 . ? O3A O3A M2A 127.9(3) 4_566 . ? SiB O3B SiB 130.8(5) 4_576 . ? SiB O3B M2A 121.9(4) 4_576 2_655 ? SiB O3B M2A 104.7(3) . 2_655 ? SiB O3B O3B 113.9(4) . 4_576 ? M2A O3B O3B 137.1(3) 2_655 4_576 ? SiB O3B O3B 161.5(3) 4_576 4_575 ? M2A O3B O3B 69.3(2) 2_655 4_575 ? O3B O3B O3B 146.1(5) 4_576 4_575 ? SiB O3B M2A 87.6(3) 4_576 3_666 ? SiB O3B M2A 79.1(3) . 3_666 ? M2A O3B M2A 122.8(4) 2_655 3_666 ? O3B O3B M2A 52.0(2) 4_576 3_666 ? O3B O3B M2A 98.1(3) 4_575 3_666 ? O2A SiA O1A 117.5(4) . 1_455 ? O2A SiA O3A 112.3(4) . 4_565 ? O1A SiA O3A 109.2(4) 1_455 4_565 ? O2A SiA O3A 101.7(4) . . ? O1A SiA O3A 109.9(4) 1_455 . ? O3A SiA O3A 105.3(4) 4_565 . ? O2B SiB O1B 117.1(4) . . ? O2B SiB O3B 109.5(4) . 4_575 ? O1B SiB O3B 107.8(4) . 4_575 ? O2B SiB O3B 104.8(4) . . ? O1B SiB O3B 108.3(4) . . ? O3B SiB O3B 109.0(4) 4_575 . ? O1A M1A O2A 94.8(3) 3_665 . ? O1A M1A O1B 176.7(3) 3_665 4_576 ? O2A M1A O1B 88.3(3) . 4_576 ? O1A M1A O2B 86.8(3) 3_665 2_645 ? O2A M1A O2B 91.5(3) . 2_645 ? O1B M1A O2B 94.4(3) 4_576 2_645 ? O1A M1A O1A 93.5(3) 3_665 2_655 ? O2A M1A O1A 91.5(3) . 2_655 ? O1B M1A O1A 85.2(3) 4_576 2_655 ? O2B M1A O1A 177.0(3) 2_645 2_655 ? O1A M1A O1B 85.2(3) 3_665 . ? O2A M1A O1B 173.7(3) . . ? O1B M1A O1B 91.7(3) 4_576 . ? O2B M1A O1B 94.8(3) 2_645 . ? O1A M1A O1B 82.2(3) 2_655 . ? O1A M1A M21 47.2(11) 3_665 4_565 ? O2A M1A M21 89.1(9) . 4_565 ? O1B M1A M21 134.3(11) 4_576 4_565 ? O2B M1A M21 40.1(12) 2_645 4_565 ? O1A M1A M21 140.5(11) 2_655 4_565 ? O1B M1A M21 95.4(8) . 4_565 ? O1A M1A M2A 138.0(3) 3_665 4_566 ? O2A M1A M2A 43.7(2) . 4_566 ? O1B M1A M2A 45.2(2) 4_576 4_566 ? O2B M1A M2A 88.3(2) 2_645 4_566 ? O1A M1A M2A 93.5(2) 2_655 4_566 ? O1B M1A M2A 136.8(2) . 4_566 ? M21 M1A M2A 113.3(7) 4_565 4_566 ? O1A M1A M2A 45.1(2) 3_665 4_565 ? O2A M1A M2A 92.9(2) . 4_565 ? O1B M1A M2A 136.1(2) 4_576 4_565 ? O2B M1A M2A 41.7(2) 2_645 4_565 ? O1A M1A M2A 138.5(2) 2_655 4_565 ? O1B M1A M2A 91.5(2) . 4_565 ? M21 M1A M2A 4.1(7) 4_565 4_565 ? M2A M1A M2A 117.26(16) 4_566 4_565 ? M21 M2A O2B 42(10) . 3_666 ? M21 M2A O2A 134(10) . 4_565 ? O2B M2A O2A 169.5(3) 3_666 4_565 ? M21 M2A O1B 127(10) . 1_545 ? O2B M2A O1B 92.2(3) 3_666 1_545 ? O2A M2A O1B 85.5(3) 4_565 1_545 ? M21 M2A O1A 70(10) . 2_645 ? O2B M2A O1A 83.1(3) 3_666 2_645 ? O2A M2A O1A 86.5(3) 4_565 2_645 ? O1B M2A O1A 81.4(3) 1_545 2_645 ? M21 M2A O3A 84(10) . 4_565 ? O2B M2A O3A 116.7(3) 3_666 4_565 ? O2A M2A O3A 67.8(3) 4_565 4_565 ? O1B M2A O3A 149.3(2) 1_545 4_565 ? O1A M2A O3A 110.6(4) 2_645 4_565 ? M21 M2A O3B 120(10) . 2_645 ? O2B M2A O3B 104.6(3) 3_666 2_645 ? O2A M2A O3B 85.7(3) 4_565 2_645 ? O1B M2A O3B 91.4(3) 1_545 2_645 ? O1A M2A O3B 169.8(2) 2_645 2_645 ? O3A M2A O3B 72.4(3) 4_565 2_645 ? M21 M2A SiA 113(10) . 4_565 ? O2B M2A SiA 151.5(2) 3_666 4_565 ? O2A M2A SiA 32.9(2) 4_565 4_565 ? O1B M2A SiA 116.2(2) 1_545 4_565 ? O1A M2A SiA 102.0(3) 2_645 4_565 ? O3A M2A SiA 35.13(19) 4_565 4_565 ? O3B M2A SiA 74.6(2) 2_645 4_565 ? M21 M2A O3B 62(10) . 3_666 ? O2B M2A O3B 58.4(2) 3_666 3_666 ? O2A M2A O3B 130.8(3) 4_565 3_666 ? O1B M2A O3B 124.4(3) 1_545 3_666 ? O1A M2A O3B 131.5(2) 2_645 3_666 ? O3A M2A O3B 69.4(3) 4_565 3_666 ? O3B M2A O3B 58.68(16) 2_645 3_666 ? SiA M2A O3B 100.4(2) 4_565 3_666 ? M2A M21 O2B 132(10) . 3_666 ? M2A M21 O1A 102(10) . 2_645 ? O2B M21 O1A 90.9(16) 3_666 2_645 ? M2A M21 M1A 134(10) . 4_566 ? O2B M21 M1A 46.1(8) 3_666 4_566 ? O1A M21 M1A 45.3(7) 2_645 4_566 ? _diffrn_measured_fraction_theta_max 0.640 _diffrn_reflns_theta_full 29.90 _diffrn_measured_fraction_theta_full 0.640 _refine_diff_density_max 0.876 _refine_diff_density_min -1.108 _refine_diff_density_rms 0.230 _diffrn_ambient_pressure 3172000 _chemical_formula_moiety 'Ca0.48 Fe4 Mg3.48 O24 Si8'