[QE-users] Elastic_constant calculations for supercell using thermo_pw.x

[Shiferaw Gadisa]

When I calculate the elastic constants for supercells of my system using
thermo_pw.x. I found the compatibility problem of ibrav. My system is
tetragonal
Please how can I solve the issue and continue my calculations?
Thank you in advance for any assistance
The input / out files of calculations are shown as follows

&INPUT_THERMO
  what='mur_lc_elastic_constants',
/
&CONTROL
                 calculation = 'scf' ,
                     pseudo_dir = './',
                         outdir='temp/'
                      prefix = 'psto50' ,
 /
 &SYSTEM
                       ibrav = 6,
                   celldm(1) = 14.74,
                   celldm(3) = 1.06,
                         nat = 20,
                        ntyp = 4,
                     ecutwfc = 40.0 ,
                        nbnd = 62,
 /
 &ELECTRONS
                    conv_thr = 1.0d-8 ,
                 mixing_mode = 'plain' ,
                 mixing_beta = 0.7 ,
             diagonalization = 'davidson' ,
 /
ATOMIC_SPECIES
   Pb  207.20000  Pb.pbe-mt_fhi.UPF
   Sn  118.70000  Sn.pbe-mt_fhi.UPF
   Ti   47.86700  Ti.pbe-mt_fhi.UPF
    O   15.99940  O.pbe-mt_fhi.UPF
ATOMIC_POSITIONS (angstrom)
Sn       0.000000000   0.000000000   0.000000000
Ti       1.995794146   2.008568413   2.009579978
O        1.984411263   2.008567974  -0.000000000
O        0.000000000   2.008568082   2.009579978
O        1.985281957   0.000000000   2.009579978
Sn       0.000000000   4.017139736   0.000000000
Ti       1.995794146   6.025711058   2.009579978
O        1.984411263   6.025711497  -0.000000000
O        0.000000000   6.025711389   2.009579978
O        1.985283246   4.017139736   2.009579978
Pb       4.016267350   0.000000000   0.000000000
Ti       6.036740554   2.008568413   2.009579978
O        6.048123437   2.008567974  -0.000000000
O        4.016267350   2.008566335   2.009579978
O        6.047252743   0.000000000   2.009579978
Pb       4.016267350   4.017139736   0.000000000
Ti       6.036740554   6.025711058   2.009579978
O        6.048123437   6.025711497  -0.000000000
O        4.016267350   6.025713136   2.009579978
O        6.047251454   4.017139736   2.009579978
K_POINTS automatic
 4  4  4  1  1  1

*Output*

 Reading input from _temporary_1
               file Pb.pbe-mt_fhi.UPF: wavefunction(s)  5f renormalized
               file Sn.pbe-mt_fhi.UPF: wavefunction(s)  5d 4f renormalized
               file Ti.pbe-mt_fhi.UPF: wavefunction(s)  4f renormalized
               file O.pbe-mt_fhi.UPF: wavefunction(s)  4f renormalized

   Info: using nr1, nr2, nr3 values from input

   Info: using nr1, nr2, nr3 values from input

     C_1 (1) is incompatible with the tetragonal Bravais lattice
     It is compatible with the
     triclinic Bravais lattice; ibrav=   14
     You might want to change the Bravais lattice or to
     understand why the symmetries are wrong before continuing
     The point group or the Laue class are not used to reduce the number of
     computed tensor components
Info: using nr1, nr2, nr3 values from input
     Computing the frozen ions elastic constants at the minimum volume
     FFT mesh: (   60,   60,   64 )

     Bravais lattice:

     ibrav=  6: tetragonal
     Cell parameters:

     alat=  14.740000 a.u., c/a=   1.060000


     Starting primitive lattice vectors:
     crystal axes: (cart. coord. in units of alat)

               a(1) = (   1.000000   0.000000   0.000000 )
               a(2) = (   0.000000   1.000000   0.000000 )
               a(3) = (   0.000000   0.000000   1.060000 )

     Starting reciprocal lattice vectors:
     reciprocal axes: (cart. coord. in units 2 pi/alat)

               b(1) = (  1.000000  0.000000  0.000000 )
               b(2) = (  0.000000  1.000000  0.000000 )
               b(3) = (  0.000000  0.000000  0.943396 )
     ......


Shiferaw G.
PhD student
Department of physics
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