Dear Li,
I had the same issue back in the days.If you start really far from equilibrium
it is usually hard to get the ground state, the way I solved it is by running a
scf for a set of celldm(1) and looking either at forces, pressure or the total
energy.
Once the approximate value of celldm is found, I runned a relax calculation and
than a vc-relax.
Hope this will work for you as well,
Cheers,
Zack
________________________________
From: users <users-boun...@lists.quantum-espresso.org> on behalf of jibiaoli
<jibia...@foxmail.com>
Sent: Friday, November 23, 2018 10:32:11 AM
To: users
Subject: [QE-users] Unit Cell goes larger and larger in variable cell geometry
optimization
Dear QE users and developers,
Recently I used vc-relax to optimize Se in the honeycomb structure, but the
unit cell goes larger and larger without convergence. To me there must be
something wrong with my calculations. Do you have any idea to get everything
right?
Best
Jibiao Li
Yangtze Normal University, China
&CONTROL
calculation = 'vc-relax' ,
restart_mode = 'from_scratch' ,
outdir = './' ,
pseudo_dir = '/home/jibiaoli/pseudo/' ,
prefix = 'Se_hc' ,
disk_io = 'high' ,
/
&SYSTEM
ibrav = 4,
celldm(1) = 4.7126,
celldm(3) = 8.41,
nat = 2,
ntyp = 1,
ecutwfc = 41 ,
ecutrho = 180 ,
occupations = 'smearing' ,
degauss = 0.05D0 ,
smearing = 'methfessel-paxton' ,
vdw_corr = 'grimme-d2' ,
/
&ELECTRONS
mixing_beta = 0.3D0 ,
diagonalization = 'david' ,
/
&IONS
ion_dynamics = 'bfgs' ,
/
&CELL
cell_dynamics = 'bfgs' ,
cell_dofree = '2Dxy' ,
/
ATOMIC_SPECIES
Se 78.96100 Se.pbe-van.UPF
ATOMIC_POSITIONS angstrom
Se 1.246899765 0.719897900 0.000000000
Se 0.000000000 0.000000000 0.000000000 0 0 0
K_POINTS automatic
9 9 1 0 0 0
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