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

[Arena Konta]

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