You cannot obtain 8 symmetry operations for a monoclinic system. C_2h is the correct point group for a system with space group C2/c. Actually the last four symmetry equivalent positions are due to the translations of the base centered monoclinic Bravais lattice. Using ibrav=-13 it is not necessary to add these atoms in the list of atoms inside the unit cell.
HTH, Andrea On Wed, 2014-12-17 at 13:08 +0000, Mutlu COLAKOGULLARI wrote: > Dear All, > I am working on a monoclinic material which has space group 15. It has C2/c > point group. > When I run the pwscf, it gives me the C2/m point group that corresponds to > the space group 12. > point group C_2h (2/m) > there are 4 classes > the character table: > E C2 i s_h > A_g 1.00 1.00 1.00 1.00 > B_g 1.00 -1.00 1.00 -1.00 > A_u 1.00 1.00 -1.00 -1.00 > B_u 1.00 -1.00 -1.00 1.00 > The symmetry operations of these two monoclinic space groups have 8 symmetry > operations. pwscf symmetry calculations found just 4...what about the other > 4? > I have checked the space groups from > "http://www.cryst.ehu.es/cryst/get_gen.html": > General Positions of the Group 12 (C2/m) [unique axis b] > 1. x,y,z > 2. -x,y,-z > 3. -x,-y,-z > 4. x,-y,z > 5. x+1/2,y+1/2,z > 6. -x+1/2,y+1/2,-z > 7. -x+1/2,-y+1/2,-z > > 8. x+1/2,-y+1/2,z > General Positions of the Group 15 (C2/c) [unique axis b] > 1. x,y,z > 2. -x,y,-z+1/2 > 3. -x,-y,-z > 4. x,-y,z+1/2 > 5. x+1/2,y+1/2,z > 6. -x+1/2,y+1/2,-z+1/2 > 7. -x+1/2,-y+1/2,-z > 8. x+1/2,-y+1/2,z+1/2 > Here is the lite-input: > > &control > calculation = 'scf', > restart_mode = 'from_scratch', > pseudo_dir = '/home//tlg2/pseudos', > outdir = './outdir', > prefix = 'TlGaSe2', > verbosity = 'high' > > / > > &system > ibrav = -13 > > celldm(1)=20.166973593 > celldm(2)=0.999721681046 > celldm(3)=1.453103256 > celldm(5)=-0.173527859407 > nat = 32 > ntyp = 3 > ecutwfc = 65 > ecutrho = 650 > / > &electrons > diagonalization = 'david' > diago_david_ndim = 8 > mixing_mode = 'plain' > mixing_beta = 0.7 > mixing_ndim = 8 > conv_thr = 1.0d-8, > / > > ATOMIC_SPECIES > Tl 204.3833 Tl.pbesol-dn-rrkjus_psl.1.0.0.UPF > Ga 69.7230 Ga.pbesol-dn-rrkjus_psl.1.0.0.UPF > Se 78.9600 Se.pbesol-dn-rrkjus_psl.1.0.0.UPF > ATOMIC_POSITIONS crystal > Tl 0.153800000000000 0.775600000000000 0.114000000000000 > Tl 0.224400000000000 0.846200000000000 0.386000000000000 > Tl 0.846200000000000 0.224400000000000 0.886000000000000 > Tl 0.775600000000000 0.153800000000000 0.614000000000000 > Tl 0.222100000000000 0.346700000000000 0.386400000000000 > Tl 0.653300000000000 0.777900000000000 0.113600000000000 > Tl 0.777900000000000 0.653300000000000 0.613600000000000 > Tl 0.346700000000000 0.222100000000000 0.886400000000000 > Se 0.946000000000000 0.054000000000000 0.250000000000000 > Se 0.054000000000000 0.946000000000000 0.750000000000000 > Se 0.426000000000000 0.574000000000000 0.250000000000000 > Se 0.574000000000000 0.426000000000000 0.750000000000000 > Se 0.145000000000000 0.269000000000000 0.071000000000000 > Se 0.731000000000000 0.855000000000000 0.429000000000000 > Se 0.855000000000000 0.731000000000000 0.929000000000000 > Se 0.269000000000000 0.145000000000000 0.571000000000000 > Se 0.952000000000000 0.572000000000000 0.252000000000000 > Se 0.428000000000000 0.048000000000000 0.248000000000000 > Se 0.048000000000000 0.428000000000000 0.748000000000000 > Se 0.572000000000000 0.952000000000000 0.752000000000000 > Se 0.736000000000000 0.360000000000000 0.438000000000000 > Se 0.640000000000000 0.264000000000000 0.062000000000000 > Se 0.264000000000000 0.640000000000000 0.562000000000000 > Se 0.360000000000000 0.736000000000000 0.938000000000000 > Ga 0.909000000000000 0.291000000000000 0.162000000000000 > Ga 0.709000000000000 0.091000000000000 0.338000000000000 > Ga 0.091000000000000 0.709000000000000 0.838000000000000 > Ga 0.291000000000000 0.909000000000000 0.662000000000000 > Ga 0.707000000000000 0.583000000000000 0.339000000000000 > Ga 0.417000000000000 0.293000000000000 0.161000000000000 > Ga 0.293000000000000 0.417000000000000 0.661000000000000 > Ga 0.583000000000000 0.707000000000000 0.839000000000000 > K_POINTS automatic > 2 2 1 1 1 1 > The primitive cell has been created by cif2cell code using the cif file as > following: > _journal_issue 12 > _journal_name_full 'Chemistry of Materials' > > _journal_page_first 3120 > _journal_volume 23 > _journal_year 2011 > _chemical_formula_structural 'Tl Ga Se2' > _chemical_formula_sum 'Ga Se2 Tl' > _chemical_name_systematic 'Thallium Gallium Selenide' > _space_group_IT_number 15 > _symmetry_Int_Tables_number 15 > _symmetry_space_group_name_Hall '-C 2yc' > _symmetry_space_group_name_H-M 'C 1 2/c 1' > _audit_creation_date 2008/02/01 > _cell_angle_alpha 90. > _cell_angle_beta 99.993(6) > _cell_angle_gamma 90. > _cell_formula_units_Z 16 > _cell_length_a 10.779(2) > _cell_length_b 10.776(1) > _cell_length_c 15.663(5) > _cell_volume 1791.7(7) > _refine_ls_R_factor_all 0.0652 > _[local]_cod_data_source_file cm200946y_si_002.cif > _[local]_cod_data_source_block 157752-ICSD > _[local]_cod_chemical_formula_sum_orig 'Ga1 Se2 Tl1' > _cod_original_cell_volume 1791.73 > _cod_database_code 4000782 > loop_ > _symmetry_equiv_pos_site_id > _symmetry_equiv_pos_as_xyz > 1 'x, -y, z+1/2' > 2 '-x, -y, -z' > 3 '-x, y, -z+1/2' > 4 'x, y, z' > 5 'x+1/2, -y+1/2, z+1/2' > 6 '-x+1/2, -y+1/2, -z' > 7 '-x+1/2, y+1/2, -z+1/2' > 8 'x+1/2, y+1/2, z' > loop_ > _atom_site_aniso_label > _atom_site_aniso_type_symbol > _atom_site_aniso_U_11 > _atom_site_aniso_U_22 > _atom_site_aniso_U_33 > _atom_site_aniso_U_12 > _atom_site_aniso_U_13 > _atom_site_aniso_U_23 > Tl1 Tl1+ 0.052(6) 0.063(5) 0.06(2) -0.022(3) 0.005(8) 0.000(5) > Tl2 Tl1+ 0.044(6) 0.044(6) 0.07(2) -0.022(3) 0.005(8) 0.002(5) > Ga1 Ga3+ 0.015(9) 0.001(6) 0.05(3) 0.009(6) 0.01(2) -0.019(9) > Ga2 Ga3+ 0.019(7) 0.037(9) 0.00(3) -0.008(9) -0.01(1) -0.01(1) > Se1 Se2- 0.03(1) 0.02(1) 0.06(5) 0. 0.02(2) 0. > Se2 Se2- 0.006(9) 0.001(7) 0.06(4) 0. -0.01(2) 0. > Se3 Se2- 0.04(1) 0.05(1) 0.01(4) 0.01(1) -0.01(2) -0.02(1) > Se4 Se2- 0.012(6) 0.021(7) 0.06(4) 0.01(1) -0.018(9) -0.018(5) > Se5 Se2- 0.05(1) 0.06(1) 0.00(4) -0.053(9) -0.01(2) -0.02(1) > loop_ > _atom_site_label > _atom_site_type_symbol > _atom_site_symmetry_multiplicity > _atom_site_Wyckoff_symbol > _atom_site_fract_x > _atom_site_fract_y > _atom_site_fract_z > _atom_site_occupancy > _atom_site_attached_hydrogens > Tl1 Tl1+ 8 f 0.4647(6) 0.3109(5) 0.1140(9) 1. 0 > Tl2 Tl1+ 8 f 0.2844(4) 0.0623(5) 0.3864(8) 1. 0 > Ga1 Ga3+ 8 f 0.100(1) 0.191(2) 0.162(2) 1. 0 > Ga2 Ga3+ 8 f 0.145(1) 0.438(1) 0.339(2) 1. 0 > Se1 Se2- 4 e 0. 0.054(2) 0.250 1. 0 > Se2 Se2- 4 e 0. 0.574(1) 0.250 1. 0 > Se3 Se2- 8 f 0.207(1) 0.062(1) 0.071(2) 1. 0 > Se4 Se2- 8 f 0.262(1) 0.310(1) 0.252(2) 1. 0 > Se5 Se2- 8 f 0.048(2) 0.312(1) 0.438(3) 1. 0 > loop_ > _atom_type_symbol > _atom_type_oxidation_number > Ga3+ 3 > Se2- -2 > Tl1+ 1 > loop_ > _citation_id > _citation_year > _citation_page_first > _citation_page_last > primary 2007 663 666 > Are there something wrong in my input file or primitive cell? > With my best wishes, > Mutlu. > > ------------------------------------------Dr. Mutlu COLAKOGULLARITrakya > Universitesi Fen FakultesiFizik Bolumu22030 Merkez-EDİRNE > _______________________________________________ > Pw_forum mailing list > [email protected] > http://pwscf.org/mailman/listinfo/pw_forum -- Andrea Dal Corso Tel. 0039-040-3787428 SISSA, Via Bonomea 265 Fax. 0039-040-3787249 I-34136 Trieste (Italy) e-mail: [email protected] 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