[Wien] case.klist_band for band structure calculation having R-3c spacegroup
Peter Blaha
pblaha at theochem.tuwien.ac.at
Tue May 17 08:54:47 CEST 2016
Selection of a MEANINGFUL "bandstructure" for these low-symmetry phases
is a non-trivial task. You have to experiment a bit and checkout which
directions are meaningful and give new information.
Gama-T-L-FB-Gama-T-L
does not sound very "meaningful" (why do you repeat Gamma-L-T ? how do
you come from T to L ??)
Yes, if you want to use the labels as in the Bilbao server, you need to
work with primitive cell.
LD(u,u,u) is a "direction", not a single point. When going from Gamma to
T (.5,.5,.5) you go along LD.
Of course, one can also the conventional cell (which is a hexagonal
cell) and select a few points: You can see
(0,0,.5) transfers to (1/6,1/6,1/6) in case.klist_band
(.5,0,.5) --> 2 2 -1 6
(.5,0,0) --> 1 1 -2 6
i.e.: the hexagonal vectors are converted anyway into the rhombohedral ones.
Important is, that you identify in your publication what the labels
mean, sometimes people even show a small BZ with their labels.
On 05/16/2016 06:34 PM, saurabh singh wrote:
> Thank you Gavin Abo,
> I got your point. As I understood from this forum discussions, for
> Rhombohedral lattice one should always use primitive basis coordinate of
> high symmetry point for generating case.klist_band using xcrysden. In my
> case compound have space group R-3c (167) and lattice parameter sqrt(3a)
> < (sqrt2c). So I generated the case.klist_band by manual labeling the
> high symmetry point in xcrysden, I have taken the high symmetric point
> coordinate in primitive basis from the bilbao server
> http://www.cryst.ehu.es/cgi-bin/cryst/programs/nph-kv-list. The band
> structure calculation have done along Gama-T-L-FB-Gama-T-L directions.
> The primitive basis coordinate used as Gama(0 0 0), T (1/2 1/2 1/2), L
> (0 1/2 0), FB (0 1/2, 1/2). I dont know what one can take the value of u
> (it should be less than or = 1 in primitive basis coordinate),If I know
> u value, I could have included one more symmetry point LD(u u u). Can
> you suggest the proper value of u. I hope that I have generated
> case.klist_band properly and calculated band structure correctly.
> Please give your comment on the way i did the band structure
> calculation, if you feel that there is any correction require then give
> your suggestion to do the correct band structure calculation
> <http://www.mail-archive.com/search?l=wien@zeus.theochem.tuwien.ac.at&q=from:%22Gavin+Abo%22>
>
> On Mon, May 16, 2016 at 12:20 PM, saurabh singh
> <saurabhiitmandi at gmail.com <mailto:saurabhiitmandi at gmail.com>> wrote:
>
> Thank you so much Peter BLAHA Sir for your valuable suggestion .
> I have another query, In the Bilbao crystallographic server the
> k-vector description is given in the two basis i.e. *Primitive basis
> and **Conventional basis *. In the user manual of Wien2k section
> 7.5.3 page 120, ix,iy,iz, defines the k-vector, where x= ix/idv etc.
> We use cartesian coordinates in units of 2π/a, 2π/b, 2π/c for P,C,F
> and B cubic, tetragonalnand orthorhombic lattices, but internal
> coordinates for H and monoclinic/triclinic lattices.
> For rhombohedral there is no suggestion given.
> Since we need to select the k-point manually in the xcrysden for
> high symmetric k-point, therefore it is very important to choose the
> correct basis coordinate. therefore I would like to know that in
> general for Rhombohedral space group, which basis coordinate
> (Primitive or Conventional) given in the Bilbao server should be
> used for making the case.klist_band.
> I have two choice in xcrysden:
> 1. Primitive Brillouin zone: if I choose this option in xcrysden to
> select the k-point coordinate then should i use the primitive basis
> coordinate of high k-point from the Bilbao server.
> 2. Conventional Brillouin zone: for this should i use the
> conventional basis coordinate from the Bilbao server.
>
> Please give your suggestion for choosing the proper basis coordinate
> of k-point for rhmbohedral lattice from Bilbao server.
>
> On Sun, May 15, 2016 at 10:48 PM, saurabh singh
> <saurabhiitmandi at gmail.com <mailto:saurabhiitmandi at gmail.com>> wrote:
>
> Dear All Wien2k users,
>
> We want to calculate the band structure of LaCoO3 compound. The
> space group of this compound is R-3c (No. 167). In the Wien2k
> user manual, it is suggested for R lattice to use rhombohedral
> coordinates. Therefore we made the case.structure file using
> lattice parameters a=b= 10.2541 Bohr, c= 24.5494, alpha=beta=90
> degree, gamma = 120 degree, and converted rhombohedral
> coordinates for each atom. When we try to make case.klist_band
> file by selecting the case.structure folder path in xcrysden, it
> says " the guessed bravais lattice type: not supported (the
> XSF's group number is 7). We tried the two different way to get
> the case.klist_band as follows:
>
> 1) Firstly, we have changed the lattice parameters in
> case.structure file in accordance to rhombohedral structure. We
> thought if the lattice parameters and atomic coordinate both
> will be accordance to rhombohedral then xcrysden can recognize
> the case.struct file. But again case.struct file does not
> recognized by xcrysden.
>
> 2) Secondly, we took the hcp.klist file given in wien2k SRC
> folder, which is as follows:
> GAMMA 0 0 0 40 2.0-0.5 1.5 Template for hcp
> structure
> 1 0 0 40 2.0
> 2 0 0 40 2.0
> 3 0 0 40 2.0
> 4 0 0 40 2.0
> 5 0 0 40 2.0
> 6 0 0 40 2.0
> 7 0 0 40 2.0
> 8 0 0 40 2.0
> 9 0 0 40 2.0
> SIGMA 10 0 0 40 2.0
> 11 0 0 40 2.0
> 12 0 0 40 2.0
> 13 0 0 40 2.0
> 14 0 0 40 2.0
> 15 0 0 40 2.0
> 16 0 0 40 2.0
> 17 0 0 40 2.0
> 18 0 0 40 2.0
> 19 0 0 40 2.0
> M 20 0 0 40 2.0
> 29 2 0 60 2.0
> 28 4 0 60 2.0
> 27 6 0 60 2.0
> 26 8 0 60 2.0
> 25 10 0 60 2.0
> 24 12 0 60 2.0
> 23 14 0 60 2.0
> 22 16 0 60 2.0
> 21 18 0 60 2.0
> K 20 20 0 60 2.0
> 19 19 0 60 2.0
> 18 18 0 60 2.0
> 17 17 0 60 2.0
> 16 16 0 60 2.0
> 15 15 0 60 2.0
> 14 14 0 60 2.0
> 13 13 0 60 2.0
> 12 12 0 60 2.0
> 11 11 0 60 2.0
> LAMBDA10 10 0 60 2.0
> 9 9 0 60 2.0
> 8 8 0 60 2.0
> 7 7 0 60 2.0
> 6 6 0 60 2.0
> 5 5 0 60 2.0
> 4 4 0 60 2.0
> 3 3 0 60 2.0
> 2 2 0 60 2.0
> 1 1 0 60 2.0
> GAMMA 0 0 0 60 2.0
> 0 0 1 20 2.0
> 0 0 2 20 2.0
> 0 0 3 20 2.0
> 0 0 4 20 2.0
> DELTA 0 0 5 20 2.0
> 0 0 6 20 2.0
> 0 0 7 20 2.0
> 0 0 8 20 2.0
> 0 0 9 20 2.0
> A 0 0 10 20 2.0
> END
>
> We renamed this hcp.klist file as case.klist_band and used it
> for band structure calculation. The calculated band structure
> gives the indirect band gap which is almost equal to the band
> gap obtained from SCF calculation.
>
> My question is, whether we can use the hcp.klist (given in
> Wien2k SRC folder) as case.klist_band for band structure
> calculation if the compound have R-3c space group and having the
> hexagonal lattice parameter and rhombohedral atomic coordinate
> in the case.struct file. Please let me know I am doing right or
> there is some different way to do it.
>
>
>
>
>
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--
P.Blaha
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-165300 FAX: +43-1-58801-165982
Email: blaha at theochem.tuwien.ac.at WIEN2k: http://www.wien2k.at
WWW: http://www.imc.tuwien.ac.at/staff/tc_group_e.php
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