<div dir="ltr"><div><div>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 <br>Please how can I solve the issue and continue my calculations? <br></div><div>Thank you in advance for any assistance <br></div><div>The input / out files of calculations are shown as follows<br></div><div><br></div><div>&INPUT_THERMO</div> what='mur_lc_elastic_constants',<br>/<br>&CONTROL<br>         calculation = 'scf' ,<br>           pseudo_dir = './',<br>             outdir='temp/'<br>           prefix = 'psto50' ,<br> /<br> &SYSTEM<br>            ibrav = 6,<br>          celldm(1) = 14.74,<br>          celldm(3) = 1.06,<br>             nat = 20,<br>            ntyp = 4,<br>           ecutwfc = 40.0 ,<br>            nbnd = 62,<br> /<br> &ELECTRONS<br>          conv_thr = 1.0d-8 ,<br>         mixing_mode = 'plain' ,<br>         mixing_beta = 0.7 ,<br>       diagonalization = 'davidson' ,<br> /<br>ATOMIC_SPECIES<br>  Pb  207.20000  Pb.pbe-mt_fhi.UPF<br>  Sn  118.70000  Sn.pbe-mt_fhi.UPF<br>  Ti  47.86700  Ti.pbe-mt_fhi.UPF<br>  O  15.99940  O.pbe-mt_fhi.UPF<br>ATOMIC_POSITIONS (angstrom)<br>Sn    0.000000000  0.000000000  0.000000000<br>Ti    1.995794146  2.008568413  2.009579978<br>O     1.984411263  2.008567974  -0.000000000<br>O     0.000000000  2.008568082  2.009579978<br>O     1.985281957  0.000000000  2.009579978<br>Sn    0.000000000  4.017139736  0.000000000<br>Ti    1.995794146  6.025711058  2.009579978<br>O     1.984411263  6.025711497  -0.000000000<br>O     0.000000000  6.025711389  2.009579978<br>O     1.985283246  4.017139736  2.009579978<br>Pb    4.016267350  0.000000000  0.000000000<br>Ti    6.036740554  2.008568413  2.009579978<br>O     6.048123437  2.008567974  -0.000000000<br>O     4.016267350  2.008566335  2.009579978<br>O     6.047252743  0.000000000  2.009579978<br>Pb    4.016267350  4.017139736  0.000000000<br>Ti    6.036740554  6.025711058  2.009579978<br>O     6.048123437  6.025711497  -0.000000000<br>O     4.016267350  6.025713136  2.009579978<br>O     6.047251454  4.017139736  2.009579978<br>K_POINTS automatic<br> 4 4 4  1 1 1</div><div><br></div><div><b>Output</b></div><div><br></div><div> Reading input from _temporary_1<br>        file Pb.pbe-mt_fhi.UPF: wavefunction(s)  5f renormalized<br>        file Sn.pbe-mt_fhi.UPF: wavefunction(s)  5d 4f renormalized<br>        file Ti.pbe-mt_fhi.UPF: wavefunction(s)  4f renormalized<br>        file O.pbe-mt_fhi.UPF: wavefunction(s)  4f renormalized<br><br>  Info: using nr1, nr2, nr3 values from input<br><br>  Info: using nr1, nr2, nr3 values from input<br><br>   C_1 (1) is incompatible with the tetragonal Bravais lattice<br>   It is compatible with the<br>   triclinic Bravais lattice; ibrav=  14<br>   You might want to change the Bravais lattice or to<br>   understand why the symmetries are wrong before continuing<br>   The point group or the Laue class are not used to reduce the number of<br>   computed tensor components</div><div>Info: using nr1, nr2, nr3 values from input<br>   Computing the frozen ions elastic constants at the minimum volume<br>   FFT mesh: (  60,  60,  64 )<br><br>   Bravais lattice:<br><br>   ibrav=  6: tetragonal<br>   Cell parameters:<br><br>   alat=  14.740000 a.u., c/a=  1.060000<br><br><br>   Starting primitive lattice vectors:<br>   crystal axes: (cart. coord. in units of alat)<br><br>        a(1) = (  1.000000  0.000000  0.000000 )<br>        a(2) = (  0.000000  1.000000  0.000000 )<br>        a(3) = (  0.000000  0.000000  1.060000 )<br><br>   Starting reciprocal lattice vectors:<br>   reciprocal axes: (cart. coord. in units 2 pi/alat)<br><br>        b(1) = (  1.000000  0.000000  0.000000 )<br>        b(2) = (  0.000000  1.000000  0.000000 )<br>        b(3) = (  0.000000  0.000000  0.943396 )<br>   ......</div><div><br></div><div><br></div><div>Shiferaw G.</div><div>PhD student</div><div>Department of physics<br></div></div>