[Pw_forum] problem with K_POINTS introduced by hand (input and output files enclosed)
Giuseppe Mattioli
giuseppe.mattioli at ism.cnr.it
Thu May 7 11:07:18 CEST 2015
Dear Manuel
> Cu 0.00000 0.00000 0.00000 0 0 0
> B 0.50000 0.50000 0.50000 0 0 0
> O 0.11111 0.11111 0.11111 0 0 0
> O 0.88889 0.88889 0.88889 0 0 0
I suppose that you should add more digits to the O positions, in order to find all the symmetries of your system. This will also affect the k-point
sampling. However, if you want to use exactly a given mesh, irrespective of the internal symmetry of atoms, you have to play with symmetry flags:
+--------------------------------------------------------------------
Variable: nosym
Type: LOGICAL
Default: .FALSE.
Description: if (.TRUE.) symmetry is not used. Note that
- if the k-point grid is provided in input, it is used "as is"
and symmetry-inequivalent k-points are not generated;
- if the k-point grid is automatically generated, it will
contain only points in the irreducible BZ for the bravais
lattice, irrespective of the actual crystal symmetry.
A careful usage of this option can be advantageous
- in low-symmetry large cells, if you cannot afford a k-point
grid with the correct symmetry
- in MD simulations
- in calculations for isolated atoms
+--------------------------------------------------------------------
+--------------------------------------------------------------------
Variable: nosym_evc
Type: LOGICAL
Default: .FALSE.
Description: if(.TRUE.) symmetry is not used but the k-points are
forced to have the symmetry of the Bravais lattice;
an automatically generated k-point grid will contain
all the k-points of the grid and the points rotated by
the symmetries of the Bravais lattice which are not in the
original grid. If available, time reversal is
used to reduce the k-points (and the q => -q symmetry
is used in the phonon code). To disable also this symmetry set
noinv=.TRUE..
+--------------------------------------------------------------------
+--------------------------------------------------------------------
Variable: noinv
Type: LOGICAL
Default: .FALSE.
Description: if (.TRUE.) disable the usage of k => -k symmetry
(time reversal) in k-point generation
+--------------------------------------------------------------------
+--------------------------------------------------------------------
Variable: no_t_rev
Type: LOGICAL
Default: .FALSE.
Description: if (.TRUE.) disable the usage of magnetic symmetry operations
that consist in a rotation + time reversal.
+--------------------------------------------------------------------
+--------------------------------------------------------------------
Variable: force_symmorphic
Type: LOGICAL
Default: .FALSE.
Description: if (.TRUE.) force the symmetry group to be symmorphic by disabling
symmetry operations having an associated fractionary translation
+--------------------------------------------------------------------
+--------------------------------------------------------------------
Variable: use_all_frac
Type: LOGICAL
Default: .FALSE.
Description: if (.TRUE.) do not discard symmetry operations with an
associated fractionary translation that does not send the
real-space FFT grid into itself. These operations are
incompatible with real-space symmetrization but not with the
new G-space symmetrization. BEWARE: do not use for phonons!
The phonon code still uses real-space symmetrization.
+--------------------------------------------------------------------
HTH
Giuseppe
On Thursday, May 07, 2015 10:31:20 AM Manuel Pérez Jigato wrote:
> hello
>
> I am a newcomer to pwscf, and I would like to report a problem with the
> K_POINTS option of the input file. When I try to input the k-points by
> hand,
> the program pwscf runs fine, but, only after generating a completely
> different set of k-points, ie, ignoring my input K-POINT data.(See attached
> file: dela.out)
> For a rhombohedral cell (ibrav 5), I have introduced in the input 10
> kpoints, which originally where generated as the probably most economic set
> (pwscf generates 32 points, but it is unclear to me whether they correspond
> to the full-zone or else, to the IBZ). I have generated the 10 k-points
> from abinit, and they are expressed in "reduced/fractional-coordinates",
> which I seem to match to the option "crystal" in K_POINTS entry of pwscf
> (for me it is important to have exactly the same k-points in both
> programs). If you look inside the output file file.out from the pwscf run,
> the first strange
> thing that turns up is "No symmetry found", and the second thing is the 32
> k-points, which, furthermore, all have the same weight, consistently with
> the full zone
>
> will you please clarify this further? in case this is a symmetry problem,
> will you please let me know where in the input file I have made a mistake?
>
> thanks a lot
>
> Manuel
>
> PS the input file is
>
> &control
> calculation='scf'
> prefix='delacubo2'
> restart_mode='from_scratch'
> pseudo_dir='./'
> outdir='./'
> tstress=.true.
> tprnfor=.true.
> /
> &system
> ibrav=5
> celldm(1)=10.85761474894d0
> celldm(4)=0.87781332d0
> nat=4
> ntyp=3
> ecutwfc=30.0D0
> occupations='smearing'
> smearing='marzari-vanderbilt'
> degauss=0.005D0
> nbnd=24
> /
> &electrons
> mixing_mode='plain'
> mixing_beta=0.7D0
> startingwfc ='atomic'
> conv_thr=1.D-08
> diagonalization='david'
> /
> ATOMIC_SPECIES
> Cu 63.546 cu.upf
> B 10.811 b.upf
> O 15.999 o.upf
> ATOMIC_POSITIONS (alat)
> Cu 0.00000 0.00000 0.00000 0 0 0
> B 0.50000 0.50000 0.50000 0 0 0
> O 0.11111 0.11111 0.11111 0 0 0
> O 0.88889 0.88889 0.88889 0 0 0
> K_POINTS (crystal)
> 10
> 1.25000000E-01 1.25000000E-01 1.25000000E-01 1
> 3.75000000E-01 1.25000000E-01 1.25000000E-01 3
> -3.75000000E-01 1.25000000E-01 1.25000000E-01 3
> -1.25000000E-01 1.25000000E-01 1.25000000E-01 3
> 3.75000000E-01 3.75000000E-01 1.25000000E-01 3
> -3.75000000E-01 3.75000000E-01 1.25000000E-01 6
> -1.25000000E-01 3.75000000E-01 1.25000000E-01 6
> -3.75000000E-01 -3.75000000E-01 1.25000000E-01 3
> 3.75000000E-01 3.75000000E-01 3.75000000E-01 1
> -3.75000000E-01 3.75000000E-01 3.75000000E-01 3
>
> -----------------------------------------------------------------------------------------------------
>
> Dr Manuel Pérez Jigato, Chargé de Recherche
> Luxembourg Institute of Science and Technology (LIST)
> Materials Research and Technology (MRT)
> 41 rue du Brill
> L-4422 BELVAUX
> Grand-Duché de Luxembourg
> Tel (+352) 47 02 61 - 584
> Fax (+352) 47 02 64
> e-mail manuel.perez at list.lu
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Giuseppe Mattioli
CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
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I 00015 - Monterotondo Stazione (RM), Italy
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