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

[Paolo Giannozzi]

I don't think weights are different; one set is normalized, one set is not,
but weights are automatically normalized inside the code

Paolo
On Thu, Mar 14, 2019 at 7:14 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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-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
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