#\#CIF_2.0
# Created by the Bilbao Crystallographic Server
# http://www.cryst.ehu.es
# Date: 11/30/2017 16:46:36
# Database entry: 1.1.37 NaFeSi2O6
# Cif-like file for the case 1.1.37


data_5yOhtAoR
_audit_creation_date            2017-11-30
_audit_creation_method          "Bilbao Crystallographic Server"

_chemical_name_systematic
;
;
_chemical_name_common                    ?
_chemical_formula_moiety                 ?
_chemical_formula_structural             ?
_chemical_formula_analytical             ?
_chemical_formula_iupac                  ?
_chemical_formula_sum                    'Na Fe Si2 O6'
_chemical_formula_weight                 ?
_chemical_melting_point                  ?
_chemical_compound_source                ?
_chemical_absolute_configuration         .


_citation_journal_abbrev        "PHYSICAL REVIEW B"
_citation_journal_volume        91
_citation_page_first            ?
_citation_page_last             ?
_citation_article_id            214415
_citation_year                  2015
_citation_DOI                   10.1103/PhysRevB.91.214415

loop_
_citation_author_name
"Baum, M"

_atomic_positions_source_database_code_ICSD  .
_atomic_positions_source_other               .

_transition_temperature     6
_experiment_temperature     1.9

loop_
_irrep_id
_irrep_dimension
_irrep_small_dimension
_irrep_direction_type
_irrep_action
_irrep_modes_number
_irrep_presence
? ? ? ? ? ? ?

_exptl_crystal_magnetic_properties_details
;
NSD
Transverse helical modulation with moment on the ac plane. Another incommensurate phase (transverse collinear) is reported between 6K and 9K (see entry #1.36)
Fourier components of the modulation for the symmetry independent Fe site are only given approximate values that roughly correspond to the parameters reported in the original reference.
Modulation: Mmax: 3.06(3), Mmin: 2.54(4), angle with c axis of major principal axis: 50 degrees, phase shift between modulation of atoms related by inversion: 0.218(2) radians.
;

_active_magnetic_irreps_details
;
1k magnetic incommensurate structure
MSSG associated with the superposition of two irrep modes for the same irrep.
The Fe site splits into two. Modulations for the two Fe sites are given equal values except for a phase shift. The phase shift indicated  in the reference does not seem to correspond to the modulation shown in the figures. 180 degrees have added to conform with the figure.
Chiral structure, polar along b. Space inversion is broken by the magnetic modulation. Type II multiferroic.
The global phase of the modulation is arbitrary and has been fixed here by choosing zero for the amplitude of the sine term of the Mx modulation of Fe1_1.
The structure has seven parameters free. The correlation introduced between the two Fe sites reduces it to four.
;

_parent_space_group.name_H-M_alt              'C 2/c'
_parent_space_group.IT_number             15
_parent_space_group.transform_Pp_abc    'a,b,c;0,0,0'

_cell_modulation_dimension               1

loop_
_cell_wave_vector_seq_id
_cell_wave_vector_x
_cell_wave_vector_y
_cell_wave_vector_z
1 0.000000 0.780000 0.000000


_parent_space_group.child_transform_Pp_abc  'a,b,c;0,0,0'

_space_group.magn_ssg_name  "C21'(0\b0)ss"
_space_group.magn_point_group_name  "21'"
_space_group.magn_point_group_number  "3.2.7"
_cell_length_a                 9.6618(5)
_cell_length_b                 8.7933(4)
_cell_length_c                 5.2946(2)
_cell_angle_alpha              90
_cell_angle_beta               107.334(3)
_cell_angle_gamma              90

loop_
_space_group_symop_magn_ssg_operation.id
_space_group_symop_magn_ssg_operation.algebraic
1 x1,x2,x3,x4,+1
2 -x1,x2,-x3+1/2,x4+1/2,+1

loop_
_space_group_symop_magn_ssg_centering.id
_space_group_symop_magn_ssg_centering.algebraic
1 x1,x2,x3,x4,+1
2 x1+1/2,x2+1/2,x3,x4,+1
3 x1,x2,x3,x4+1/2,-1
4 x1+1/2,x2+1/2,x3,x4+1/2,-1

loop_
_atom_site_label
_atom_site_type_symbol
_atom_site_fract_x
_atom_site_fract_y
_atom_site_fract_z
_atom_site_occupancy
Na1_1 Na 0 0.3002 0.25 1
Na1_2 Na 0 -0.3002 -0.25 1
Fe1_1 Fe 0 0.8994 0.25 1
Fe1_2 Fe 0 -0.8994 -0.25 1
Si1_1 Si 0.2905 0.0903 0.2379 1
Si1_2 Si -0.2905 -0.0903 -0.2379 1
O1_1 O 0.1137 0.0796 0.1384 1
O1_2 O -0.1137 -0.0796 -0.1384 1
O2_1 O 0.3595 0.2551 0.3041 1
O2_2 O -0.3595 -0.2551 -0.3041 1
O3_1 O 0.3526 0.0089 0.0105 1
O3_2 O -0.3526 -0.0089 -0.0105 1


loop_
_atom_site_moment.label
_atom_site_moment.crystalaxis_x
_atom_site_moment.crystalaxis_y
_atom_site_moment.crystalaxis_z
_atom_site_moment.symmform
Fe1_1 0 0 0 0,0,0
Fe1_2 0 0 0 0,0,0

loop_
_atom_site_Fourier_wave_vector.seq_id
_atom_site_Fourier_wave_vector.q1_coeff
1 1

loop_
_atom_site_moment_Fourier.atom_site_label
_atom_site_moment_Fourier.axis
_atom_site_moment_Fourier.wave_vector_seq_id
_atom_site_moment_Fourier_param.cos
_atom_site_moment_Fourier_param.sin
_atom_site_moment_Fourier_param.cos_symmform
_atom_site_moment_Fourier_param.sin_symmform
Fe1_1 x 1 2.99 0 mxc1 mxs1
Fe1_1 y 1 0 0 0 0
Fe1_1 z 1 1.10 -3.13 mzc1 mzs1
Fe1_2 x 1 -2.92 0.65 mxc1 mxs1
Fe1_2 y 1 0 0 0 0
Fe1_2 z 1 -0.39 3.30 mzc1 mzs1


