[Thermo_pw-forum] mur_lc stpes and ibrav

[Andrea Dal Corso]

The structure has not the minimum number of symmetries required for a  
cubic structure. Please check the QE
user's guide for the FAQ: why the code does not find all the  
symmetries that I expect.

Andrea
Quoting Ahmed Sherif Omran <microomran at gmail.com>:

> Dear Thermo_pw users,
>
> I am new to therm_pw.I am trying to do lattice parameter calculation (and
> later elastic constants) for sI clathrate hydrate (46 water molecule+8
> guest gases).The structure is a cubic.
>
> The input file:
> scf.in
> &CONTROL
>   title = 'SI_8CO2_Relax'
>   pseudo_dir = '.'
>   !outdir = './outdir'
>   calculation = 'relax'
>   nstep=50
>   etot_conv_thr = 1e-4
>   forc_conv_thr = 1e-4
>  max_seconds=82500
> /
>
> &SYSTEM
>   A = 12.029999733000
>   nat= 162
>   ntyp= 3
>   ibrav= 1
>   ecutwfc= 55.0
>   ecutrho = 440.0
> !ecuthro=8-10*ecutwfc
> !occupations='smearing'
> !gaussian smearing
>   smearing='gaussian'
> !ordinary Gaussian spreading (Default)
>   degauss= 0.022
>   input_dft= 'vdw-df2'
> /
>
> &ELECTRONS
>   mixing_beta = 0.7
>   conv_thr =  1.0d-08
>   diagonalization='david'
>   electron_maxstep = 150
> /
>
> &IONS
> /
>
> &CELL
> /
>
> ATOMIC_SPECIES
> C   12.011  C.pbe-n-kjpaw_psl.1.0.0.UPF
> H    1.008  H.pbe-kjpaw_psl.1.0.0.UPF
> O   15.999  O.pbe-n-kjpaw_psl.0.1.UPF
>
> ATOMIC_POSITIONS (angstrom)
> C             5.6914623648        6.3477925243        9.0385162417
> C             6.0203188824        0.0140445035        6.0076929324
> C             0.0103067680        6.0124985177        0.0271263591
> C             0.5255489420        9.0628026901        5.6877293485
> C            -0.5089082791        2.9502728029        6.3664117395
> C             2.9707134143        0.1359390055        0.0057036813
> C             9.0362791318        0.2927456487       -0.2246132818
> C             6.3078182653        5.6844139347        2.9923046100
> H             7.6681600210        8.8103809640        5.1812970528
> H             7.9474183614        7.5109661777        6.0550379444
> H             8.0588580146        9.3162094407        7.4168881942
> H             8.0234619914        2.8265464617        7.5198466803
> H            -0.9928948776        2.8873069490        1.7034973611
> H             8.4213026994        5.2152049586        6.1694929950
> H             8.5729430479        1.3775298181        4.1473499668
> ...
> O            -0.0990445262        0.0367157095        2.9958286391
> O             5.2088485235       -0.1956393873        5.1874258136
> K_POINTS automatic
> 2 2 2  0 0 0
>
> thermo_control
> &INPUT_THERMO
>   what='mur_lc',
>   lmurn=.FALSE.,
>   frozen_ions=.FALSE.
>  /
> thermo_control (END)
>
>
> I encountered the following problems:
>
> 1-The code did not recognize that the structure is cubic and assigin it to
> triclinic Bravais lattice; ibrav=   14
>
> -----------
>   Program THERMO_PW v.6.5 starts on 18Jul2021 at  9:31:41
>
>      This program is part of the open-source Quantum ESPRESSO suite
>      for quantum simulation of materials; please cite
>          "P. Giannozzi et al., J. Phys.:Condens. Matter 21 395502 (2009);
>          "P. Giannozzi et al., J. Phys.:Condens. Matter 29 465901 (2017);
>           URL http://www.quantum-espresso.org",
>      in publications or presentations arising from this work. More details
> at
>      http://www.quantum-espresso.org/quote
>
>      Parallel version (MPI), running on   168 processors
>
>      MPI processes distributed on     6 nodes
>      K-points division:     npool     =       2
>      R & G space division:  proc/nbgrp/npool/nimage =      84
>      Reading input from _temporary_1
> Warning: card &CELL ignored
>      IMPORTANT: XC functional enforced from input :
>      Exchange-correlation= VDW-DF2
>                            (   1   4  13   0   2   0   0)
>      Any further DFT definition will be discarded
>      Please, verify this is what you really want
>
>                file C.pbe-n-kjpaw_psl.1.0.0.UPF: wavefunction(s)  2S 2P
> renormalized
>                file H.pbe-kjpaw_psl.1.0.0.UPF: wavefunction(s)  1S
> renormalized
>                file O.pbe-n-kjpaw_psl.0.1.UPF: wavefunction(s)  2P
> renormalized
>
>    Info: using nr1, nr2, nr3 values from input
>
>      C_1 (1) is incompatible with the simple cubic 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
>
>
>      Calculating the volume that minimizes the energy
>
>      FFT mesh: (  160,  160,  160 )
>
>      Bravais lattice:
>
>      ibrav=  1: simple cubic
>      Cell parameters:
>  alat=  22.733405 a.u.
>
>
>      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   1.000000 )
>
>      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  1.000000 )
>
> 2-The maximum ionic relaxation steps did not exceed the default 20 steps
> although I have specified 50 in the input file, so some geometries were not
> relaxed.
>
>
> Your help is appreciated
> Regards,
> Ahmed OMRAN
> *Researcher*
>
> *Laboratoire Catalyse et Spectrochemie (LCS)*
> France