[QE-users] issue with fixed ibrva vc-relax calculation

[rekha sharma]

Dear Users

I have been doing a vc-relax calculation of a binary compound with AB2
structure that is occupying a triclinic space group with ibrav=14.
I used QE version 6.5.

To keep the ibrav 14 from in the final vc-relax structure,  I performed the
vc-relax with celld_dofree='ibrav'
Job has been finished without any warning or error. The final geometry is
mentioned in appendix-A in below to this query.

If I choose the CELL_PARAMETERS and ATOMIC_POSITIONS from above output and
update the case.in file then it gives me ibrav= -13.

I am wondering whether I can choose celldm(1) to celldm(6) and
ATOMIC_POSITIONS from the appendix-A?

Are these celldm's final relaxed cell_parameters?

Please guide me for the above two queries.

Thank you very much

Regards
Rekha


             Appendix-A


ibrav =     14
 celldm(1) =      7.46334414
 celldm(2) =      0.99999702
 celldm(3) =      1.79237850
 celldm(4) =      0.11014359
 celldm(5) =      0.10863152
 celldm(6) =      0.24294684
Input lattice vectors:
     1.00112336     0.00000000     0.00000000
     0.24321903     0.97112641     0.00000000
     0.19492754     0.15492538     1.77703235
New lattice vectors in INITIAL alat:
     1.00112336     0.00000000     0.00000000
     0.24321903     0.97112641     0.00000000
     0.19492754     0.15492538     1.77703235
New lattice vectors in NEW alat (for information only):
     1.00000000     0.00000000     0.00000000
     0.24294611     0.97003671     0.00000000
     0.19470881     0.15475153     1.77503835
Discrepancy in bohr =     0.000000    0.000000    0.000000

     bfgs converged in   4 scf cycles and   3 bfgs steps
     (criteria: energy <  1.0E-04 Ry, force <  1.0E-03Ry/Bohr, cell <
 5.0E-01kbar)

     End of BFGS Geometry Optimization

     Final enthalpy =     -68.4522400954 Ry
Begin final coordinates
     new unit-cell volume =    715.80761 a.u.^3 (   106.07174 Ang^3 )
     density =      4.43480 g/cm^3

CELL_PARAMETERS (alat=  7.45496956)
   1.001123355   0.000000000   0.000000000
   0.243219029   0.971126408   0.000000000
   0.194927536   0.154925376   1.777032345

ATOMIC_POSITIONS (crystal)
A            0.0000235084       -0.0000109097        0.0000009223
B            0.9616465677        0.4631487680        0.2331366069
B            0.5360299239        0.0391621417        0.7668624708
End final coordinates


                                                           Appendix- B


&CONTROL
  calculation='vc-relax',
  outdir='./tmp',
  prefix='scf',
  pseudo_dir='.',
  verbosity='low',
etot_conv_thr = 0.0001
forc_conv_thr = 0.001
    nstep = 400
  tstress = .true.
  tprnfor = .true.

/

&SYSTEM
  ibrav=14,
  celldm(1)=7.4549695614d0, celldm(2)=1.0000000000d0,
celldm(3)=1.7936628644d0,
  celldm(4)=0.1100812622d0, celldm(5)=0.1085198771d0,
celldm(6)=0.2422605780d0,
  nat=3,
  ntyp=2,
  ecutwfc=50,
  ecutrho=500,

/

&ELECTRONS
  conv_thr=1d-010,
  mixing_beta=0.3d0,
/
&IONS
/
&CELL
cell_dofree='ibrav'
/

ATOMIC_SPECIES
   A  A.pbe-n-rrkjus_psl.1.0.0.UPF
   B  B.pbe-n-rrkjus_psl.1.0.0.UPF

ATOMIC_POSITIONS {crystal}
  A   0.0000000000d0   0.0000000000d0   0.0000000000d0
  B   0.9617000000d0   0.4632000000d0   0.2330000000d0
  B   0.5360000000d0   0.0391000000d0   0.7670000000d0

K_POINTS {automatic}
  11 11 5 0 0 0

-- 




Best wishes

Ms. Rekha
Teaching Assistant,
Department of Physics
RK college, Jaipur, India
Mob.: +11 91-95 790 71 697
Email: rekha1997jpr at gmail.com
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