[QE-users] Problem with generating q-points for lambda

[Hari Paudyal]

Hi,

I think, you are on the correct way, but you are taking double points on
every k-points (if you add all it is 128 but it should be 4x4x4 = 64). So,
take half on each. This can be understood by considering the Gamma (0.0 0.0
0.0) point only, there should be only one Gamma point, no?

Best,
Hari Paudyal
SUNY Binghamton University

On Thu, Mar 14, 2019 at 2:14 PM Arena Konta <qe6user at gmail.com> wrote:

> Dear Professors Paolo and and Hari,
>
> I appreciate your both help. However, I am still a little bit confused
> which weights should I chose for lambda.x file. For example:
>
> bravais-lattice index     =            7
>      lattice parameter (alat)  =       7.9506  a.u.
>      unit-cell volume          =     591.7416 (a.u.)^3
>
>      celldm(1)=   7.950626  celldm(2)=   0.000000  celldm(3)=   2.354822
>      celldm(4)=   0.000000  celldm(5)=   0.000000  celldm(6)=   0.000000
>
> scf calculations on the mesh 4x4x4 give me:
>
> number of k points=    13  Marzari-Vanderbilt smearing, width (Ry)=  0.0200
>                        cart. coord. in units 2pi/alat
>         k(    1) = (   0.0000000   0.0000000   0.0000000), wk =
> 0.0312500 = 2
>         k(    2) = (  -0.2500000   0.0000000   0.1061651), wk =
> 0.2500000 = 16
>         k(    3) = (   0.5000000   0.0000000  -0.2123303), wk =
> 0.1250000 = 8
>         k(    4) = (  -0.2500000   0.2500000   0.2123303), wk =
> 0.2500000 = 16
>         k(    5) = (   0.5000000   0.2500000  -0.1061651), wk =
> 0.5000000 = 32
>         k(    6) = (   0.2500000   0.2500000   0.0000000), wk =
> 0.1250000 = 8
>         k(    7) = (   0.5000000  -0.5000000  -0.4246605), wk =
> 0.0625000 = 4
>         k(    8) = (   0.0000000   0.0000000   0.2123303), wk =
> 0.0625000 = 4
>         k(    9) = (   0.7500000   0.0000000  -0.1061651), wk =
> 0.2500000 = 16
>         k(   10) = (   0.5000000   0.0000000   0.0000000), wk =
> 0.1250000 = 8
>         k(   11) = (   0.7500000  -0.7500000  -0.4246605), wk =
> 0.1250000 = 8
>         k(   12) = (   0.5000000  -0.5000000  -0.2123303), wk =
> 0.0625000 = 4
>         k(   13) = (   0.0000000   0.0000000  -0.4246605), wk =
> 0.0312500 = 2
> (there is no inversion in crystal structure)
>
> ph.x calculations are following:
>
>         Dynamical matrices for ( 4, 4, 4)  uniform grid of q-points
>      (  13q-points):
>        N         xq(1)         xq(2)         xq(3)
>        1   0.000000000   0.000000000   0.000000000
>        2  -0.250000000   0.000000000   0.106165127
>        3   0.500000000  -0.000000000  -0.212330253
>        4  -0.250000000   0.250000000   0.212330253
>        5   0.500000000   0.250000000  -0.106165127
>        6   0.250000000   0.250000000   0.000000000
>        7   0.500000000  -0.500000000  -0.424660507
>        8   0.000000000   0.000000000   0.212330253
>        9   0.750000000  -0.000000000  -0.106165127
>       10   0.500000000  -0.000000000   0.000000000
>       11   0.750000000  -0.750000000  -0.424660507
>       12   0.500000000  -0.500000000  -0.212330253
>       13   0.000000000  -0.000000000  -0.424660507
>
> Therefore, we can say that both q- and k-meshes are "exactly" the same in
> scf and ph calculations. However, when I generate k-mesh using kpoints.x,
> the set is equivalent, but the weights and order are different:
>
>
>
>        ***************************************************
>      *                                                 *
>      *       Welcome to the special points world!      *
>      *________________________________________________ *
>      *    1 = cubic p (sc )      8 = orthor p (so )    *
>      *    2 = cubic f (fcc)      9 = orthor base-cent. *
>      *    3 = cubic i (bcc)     10 = orthor face-cent. *
>      *    4 = hex & trig p      11 = orthor body-cent. *
>      *    5 = trigonal   r      12 = monoclinic  p     *
>      *    6 = tetrag p (st )    13 = monocl base-cent. *
>      *    7 = tetrag i (bct)    14 = triclinic   p     *
>      ***************************************************
>
>      bravais lattice  >> 7
>      filout [mesh_k]  >> TEST
>      enter celldm(3)  >> 2.35482
>      mesh: n1 n2 n3   >> 4 4 4
>      mesh: k1 k2 k3 (0 no shift, 1 shifted) >> 0 0 0
>      write all k? [f] >>
>
>      # of k-points   ==    13  of    64
>
>
>       13
>     1   0.0000000  0.0000000  0.0000000   1.00
>     2   0.2500000 -0.2500000  0.0000000   4.00
>     3   0.5000000 -0.5000000  0.0000000   2.00
>     4   0.0000000  0.2500000  0.1061652   8.00
>     5   0.5000000 -0.2500000  0.1061652  16.00
>     6   0.0000000  0.5000000  0.2123305   4.00
>     7   0.2500000  0.2500000  0.2123305   8.00
>     8   0.0000000  0.0000000  0.2123305   2.00
>     9   0.5000000 -0.5000000  0.2123305   2.00
>    10   0.0000000  0.2500000  0.3184957   8.00
>    11   0.0000000  0.5000000  0.4246609   4.00
>    12   0.2500000  0.2500000  0.4246609   4.00
>    13   0.0000000  0.0000000  0.4246609   1.00
>
> Which weights should I use in my el-ph calculations?
>
>
> --
> with regards
>
> Arena Konta
> The Institute of Thermophysics in Novosibirsk Scientific Center
>
>
>
>
>
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