[QE-users] Unit Cell goes larger and larger in variable cell geometry optimization

[jibiaoli]

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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