############################################################################## # Example file to accompany the CIF dictionary for modulated structures # ############################################################################## # Example: A misfit compound (LaS)1.14 NbS2 # # This is a CIF example corresponding to the modulated structure of # the inorganic misfit layer compound (LaS)1.14NbS2. # Data have been extracted from the already published paper: # # Superspace-Group Approach to the Modulated Structure of the Inorganic # Misfit Layer Compound (LaS)1.14NbS2 # by Sander van Smaalen # J. Phys.: Condens. Matter, (1991), 3, 1247 # # Any line starting with the symbol '#' is considered as a comment. ############################################################################## data_LaSNbS2 _audit_block_code 1997-07-24|LaSNbS2|G.M.| _audit_creation_date 1998-12-27 _audit_creation_method 'using a text processor from published results' _audit_conform_dict_name cif_ms.dic _audit_conform_dict_version 1.0 #----------------------------------------------------------------------------- # Chemical information #----------------------------------------------------------------------------- _chemical_formula_analytical 'La1.14 Nb S3.14' _chemical_formula_weight 351.93 #----------------------------------------------------------------------------- # The next items are neccessary, basically, to check the # consistency of the CIF. An extra Miller index is expected. #----------------------------------------------------------------------------- _exptl_crystal_type_of_structure 'comp' _cell_subsystems_number 2 _cell_modulation_dimension 1 _cell_reciprocal_basis_vect_number 4 #----------------------------------------------------------------------------- # NbS2 subsystem has been chosen as reference, i.e., its W matrix is the unit # matrix. #----------------------------------------------------------------------------- loop_ _cell_subsystem_code _cell_subsystem_description _cell_subsystem_matrix_W_1_1 _cell_subsystem_matrix_W_1_4 _cell_subsystem_matrix_W_2_2 _cell_subsystem_matrix_W_3_3 _cell_subsystem_matrix_W_4_1 _cell_subsystem_matrix_W_4_4 NbS2 '1-st subsystem' 1 0 1 1 0 1 LaS '2-nd subsystem' 0 1 1 1 1 0 #----------------------------------------------------------------------------- # Extended reciprocal cell. Order is important. It defines the order of # Miller indices. #----------------------------------------------------------------------------- _cell_reciprocal_basis_description ; a1*,b1*,c1* (reciprocal basis spanning the reciprocal basis of the first subsystem), a2* reciprocal axis corresponding to the second subsystem. ; #----------------------------------------------------------------------------- # The next cell parameters are those of the NbS2 subsystem. The cell parameters # of the other subsystem can be calculated with the W matrices and the wave # vectors #----------------------------------------------------------------------------- _cell_length_a 3.310 _cell_length_b 5.793 _cell_length_c 23.043 _cell_angle_alpha 90.00 _cell_angle_beta 90.00 _cell_angle_gamma 90.00 _cell_volume 441.85 _diffrn_symmetry_description ; The whole diffraction pattern shows orthorhombic symmetry. The following extinction rules were detected: hklm h+k+m=odd hklm h+l =odd hklm k+l+m=odd hk0m h+k =odd hk0m m =odd Extinction rules are compatible with the superspace groups: P:Fmmm:-11s(\a,0,0) P:Fm2m:-1-1s(\a,0,0) ; #----------------------------------------------------------------------------- # Superspace group. This susperspace group characterises the symmetry of the # global structure. It coincides with that of the NbS2 subsystem. The other # superspace group can be calculated through the W matrices #----------------------------------------------------------------------------- _space_group_ssg_name_WJJ 'P:F m 2 m:-1 -1 s' _diffrn_radiation_source 'X-ray tube' _diffrn_reflns_satellite_order_max 2 loop_ _diffrn_reflns_class_description _diffrn_reflns_class_code 'main reflections' 'Main' 'common main reflections' 'Com' 'NbS2 part' 'NbRefls' 'LaS part' 'LaRefls' 'first-order satellites' 'Sat1' 'second-order satellites' 'Sat2' # In the next entry \s stands for sigma. _reflns_observed_criterion 'I>2.5\s(I) for any reflection class' _reflns_number_observed 860 loop_ _reflns_class_number_gt _reflns_class_code 584 'Main' 226 'Sat1' 50 'Sat2' #----------------------------------------------------------------------------- # Computing section #----------------------------------------------------------------------------- _computing_structure_refinement 'COMPREF (Petricek)' #----------------------------------------------------------------------------- # The coordinates given below are referred to the direct axes of each subsystem. #----------------------------------------------------------------------------- loop_ _atom_site_label _atom_site_subsystem_code _atom_site_fract_x _atom_site_fract_y _atom_site_fract_z _atom_site_thermal_displace_type _atom_site_refinement_flags _atom_site_displace_modulation_flag Nb1 Nbs2 0 -0.0751(6) 0 Uani S yes S1 Nbs2 0 0.2583(8) 0.0678(2) Uani S yes La1 LaS 0 0.0 0.32633(5) Uani S yes S2 LaS 0 0.5086(22) 0.3003(2) Uani S yes #----------------------------------------------------------------------------- # Modulation parameters #----------------------------------------------------------------------------- _refine_ls_mod_func_description ; Displacive modulation. Fourier series. ; #----------------------------------------------------------------------------- # Modulation wave vector. Here is expressed the modulation wave vector # a2*, in the three-dimensional reciprocal basis of the first subsystem. #----------------------------------------------------------------------------- loop_ _cell_wave_vector_seq_id _cell_wave_vector_x 1 0.568 # The wave wectors corresponding to the modulation of the LaS subsystem can be # deduced using the W matrices. loop_ _atom_site_Fourier_wave_vector_seq_id _atom_site_Fourier_wave_vector_x _atom_site_Fourier_wave_vector_z _atom_site_Fourier_wave_vector_description 1 0.568 0 'First harmonic expressed in the basis of the first subsystem' 2 1.136 0 'Second harmonic expressed in the basis of the first subsystem' 3 1.761 0.5 'First harmonic expressed in the basis of the second subsystem' 4 3.522 1.0 'Second harmonic expressed in the basis of the second subsystem' # The modulation coefficients given below are referred to each subsystem. loop_ _atom_site_displace_Fourier_id _atom_site_displace_Fourier_atom_site_label _atom_site_displace_Fourier_axis _atom_site_displace_Fourier_wave_vector_seq_id Nb_NbS2_z1 Nb1 z 1 Nb_NbS2_x2 Nb1 x 2 Nb_NbS2_y2 Nb1 y 2 S_NbS2_x1 S1 x 1 S_NbS2_y1 S1 y 1 S_NbS2_z1 S1 z 1 S_NbS2_x2 S1 x 2 S_NbS2_y2 S1 y 2 S_NbS2_z2 S1 z 2 La_LaS_x3 La1 x 3 La_LaS_y3 La1 y 3 La_LaS_z3 La1 z 3 La_LaS_x4 La1 x 4 La_LaS_y4 La1 y 4 La_LaS_z4 La1 z 4 S_LaS_x3 S2 x 3 S_LaS_y3 S2 y 3 S_LaS_z3 S2 z 3 S_LaS_x4 S2 x 4 S_LaS_y4 S2 y 4 S_LaS_z4 S2 z 4 loop_ _atom_site_displace_Fourier_param_id _atom_site_displace_Fourier_param_cos _atom_site_displace_Fourier_param_sin Nb_NbS2_z1 -0.0006(2) 0. Nb_NbS2_x2 0. 0.0078(17) Nb_NbS2_y2 -0.0014(7) 0. S_NbS2_x1 0. -0.0134(85) S_NbS2_y1 -0.0022(12) 0. S_NbS2_z1 0.0014(14) 0. S_NbS2_x2 0. -0.0129(27) S_NbS2_y2 -0.0073(27) 0. S_NbS2_z2 -0.0012(3) 0. La_LaS_x3 0. -0.0010(22) La_LaS_y3 0.0174(4) 0. La_LaS_z3 -0.0005(3) 0. La_LaS_x4 0. 0.0144(7) La_LaS_y4 0.0001(14) 0. La_LaS_z4 0.0008(3) 0. S_LaS_x3 0. 0.0059(70) S_LaS_y3 0.0081(16) 0. S_LaS_z3 0.0009(12) 0. S_LaS_x4 0. -0.0030(30) S_LaS_y4 0.0002(56) 0. S_LaS_z4 0.0007(10) 0. _refine_special_details ; y-coordinate of La1 atom was not refined to fix the origin ; _refine_ls_R_factor_all 0.064 loop_ _refine_ls_class_R_factor_gt _refine_ls_class_code 0.057 'Main' 0.074 'Com' 0.064 'NbRefls' 0.046 'LaRefls' 0.112 'Sat1' 0.177 'Sat2' #----------------------------------------------------------------------------- # List of reflections. #----------------------------------------------------------------------------- loop_ _refln_index_h _refln_index_k _refln_index_l _refln_index_m_1 _refln_F_meas _refln_F_calc _refln_F_sigma _refln_observed_status _refln_scale_group_code # Next question marks are included for consistency ? ? ? ? ? ? ? ? ? # More reflections here ... #----------------------------------------------------------------------------- # Items concerning publication data #----------------------------------------------------------------------------- loop_ _citation_id _citation_title _citation_journal_abbrev _citation_journal_volume _citation_page_first _citation_page_last _citation_year primary ; Superspace-group approach to the modulated structure of the inorganic misfit layer compound (LaS)1.14NbS2 ; 'J. Phys.: Condens. Matter' 3 1247 1263 1991 loop_ _citation_author_citation_id _citation_author_name primary 'van Smaalen, S.' ##############################################################################