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'