[QE-users] vc-relax

[Sai Pavan Chitta]

Dear Sabike,

In my experience of working with monolayers, I found that the number of
k-points in the k-mesh in z direction aalso affects the convergence. The
energy starts converging the moment I increase the number of k-points in
z-direction. It also makes sense as you are using two monolayers in your
model and thus requires more k-points in the z-direction.

Moreover, you can make the convergence threshold more stringent to about
1e-8 for a proper convergence.

Regards
Chitta Sai Pavan
IIT Gandhinagar


On Tue, 9 Oct 2018, 08:18 Sabike Ghasemi, <s.ghasemi at du.ac.ir> wrote:

> dear all
> i want to relax atomic coordinates and lattic constants for graphene
> bilayer. but it dosen't converge.
> input file is:
>
>
>  &CONTROL
>                        title = GRAPHENEBILAYER ,
>                  calculation = 'vc-relax' ,
>                 restart_mode = 'from_scratch' ,
>                   wf_collect = .true. ,
>                       outdir = './out' ,
>                       wfcdir = './out' ,
>                   pseudo_dir = './' ,
>                       prefix = 'GBI' ,
>                    verbosity = 'high' ,
>                etot_conv_thr = 1.0D-4 ,
>                forc_conv_thr = 1.0D-4 ,
>                      tstress = .true. ,
>                      tprnfor = .true. ,
>  /
>  &SYSTEM
>                        ibrav = 4,
>                    celldm(1) = 4.648726,
>                    celldm(3) = 9.512195384,
>                          nat = 4,
>                         ntyp = 1,
>                      ecutwfc = 50 ,
>                      ecutrho = 500 ,
>                        nosym = .false. ,
>                  occupations = 'smearing' ,
>                      degauss = 0.002 ,
>                     smearing = 'gaussian' ,
>  /
>  &ELECTRONS
>             electron_maxstep = 200,
>                     conv_thr = 1.0D-6 ,
>                  mixing_beta = 0.3 ,
>              diagonalization = 'david' ,
>  /
>  &IONS
>                 ion_dynamics = 'bfgs' ,
>  /
>  &CELL
>                cell_dynamics = 'bfgs' ,
>                  cell_factor = 2.D0 ,
>                  cell_dofree = '2Dxy' ,
>  /
> ATOMIC_SPECIES
>     C   12.00000  C.blyp-mt.UPF
> ATOMIC_POSITIONS crystal
>     C      0.333333330    0.666666660    0.572649573
>     C      1.000000000    0.000000000    0.572649753
>     C      0.666666660    0.333333330    0.427350427
>     C      1.000000000    0.000000000    0.427350427
> K_POINTS automatic
>   16 16 1   0 0 0
>
>
> best,
> sabike
> _______________________________________________
> users mailing list
> users at lists.quantum-espresso.org
> https://lists.quantum-espresso.org/mailman/listinfo/users
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20181009/c4520194/attachment.html>