[QE-users] Getting convergence on a cell obtained from a cif using vc-relax

Fri Jun 1 16:20:52 CEST 2018

Dear folks,

I usually help some experimentalist fellows from the Center I belong 
by calculating geometries, cell parameters, vibrational frequencies, 
electronic transitions, etc, of transition metal complexes. As the 
cif file is often available, I use it to create the input file for 
PWScf using Virtual Nano Lab from Quantum Wise.

Although convergence of the vc-relax job is usually achieved, some 
cases are more problematic. Job ends with a high pressure and with 
atomic forces far from thresholds when 'bfgs' is used both for &ions 
and &cell namelists. Using 'damp' does not help to get geometry and 
cell parameters optimized. Thus my (very general) question is: does 
anybody know an strategy to systematically get convergence when 
doing vc-relax? A link to a tutorial or a document is welcome.

For completeness, the input of one of the problematic cases is 
appended below. By the way, I'm using "Program PWSCF v.6.1 (gpu tag 
v1.0)" compiled with PGI compilers and MKL libraries on a CentOS box 
with a Titan X (Pascal) gpu.

Thanks in advance

Reinaldo
Center of Inorganic Chemistry
Natl Univ of La Plata, Argentina

Input follows....

&CONTROL
  title         = 'Cu-ovatpnh2'
  calculation   = 'vc-relax'
  restart_mode  = 'from_scratch'
  outdir        = './'
  pseudo_dir    = './'
  prefix        = 'Cu-ovatpnh2'
  etot_conv_thr = 0.0001
  forc_conv_thr = 0.0004
  tstress       = .true.
  tprnfor       = .true.
  nstep         = 200
/

&SYSTEM
   ibrav       = 14
   celldm(1)   = 9.9320792573d0
   celldm(2)   = 2.0161515879d0
   celldm(3)   = 2.1156030541d0
   celldm(4)   = -0.1705259449d0
   celldm(5)   = -0.0219091103d0
   celldm(6)   = -0.2238523262d0
   nat         =  59
   ntyp        =   6
   ecutwfc     =  40
   ecutrho     = 200
   input_dft   = 'pbe'
   occupations = 'smearing'
   smearing    = 'mv'
   degauss     = 0.005
   nspin       = 2
   starting_magnetization(1) = 0.7
/

&ELECTRONS
   conv_thr        = 1d-06
   mixing_beta     = 0.6
   mixing_mode     = 'plain'
   mixing_ndim     = 8
   diagonalization = 'david'
/

&IONS
  ion_dynamics = 'bfgs'
/

&CELL
  cell_dynamics = 'bfgs'
  press         = 0.5
/

ATOMIC_SPECIES
   Cu 63.546000d0 cu_pbe_v1.2.uspp.F.UPF
   C  12.010700d0  c_pbe_v1.2.uspp.F.UPF
   H   1.007940d0  h_pbe_v1.4.uspp.F.UPF
   N  14.006700d0  n_pbe_v1.2.uspp.F.UPF
   O  15.999400d0  o_pbe_v1.2.uspp.F.UPF
   S  32.065000d0  s_pbe_v1.4.uspp.F.UPF

ATOMIC_POSITIONS (crystal)
C        0.082231085   0.204570350   0.616545553
C        0.917768915   0.795429650   0.383454447
C        0.172973917   0.203448044   0.733466608
C        0.827026083   0.796551956   0.266533392
H        0.367673209   0.258122966   0.770942028
H        0.632326791   0.741877034   0.229057972
C        0.987334077   0.125087827   0.797766960
C        0.012665923   0.874912173   0.202233040
H        1.019591574   0.112838755   0.892010655
H       -0.019591574   0.887161245   0.107989345
C        0.756454381   0.067986708   0.729401520
C        0.243545619   0.932013292   0.270598480
H        0.580696185   0.004985342   0.755622580
H        0.419303815   0.995014658   0.244377420
C        0.224564542   0.266351629   0.518206870
C        0.775435458   0.733648371   0.481793130
H        0.388829444   0.346391746   0.560989945
H        0.611170556   0.653608254   0.439010055
H        0.304022379   0.192372172   0.457292153
H        0.695977621   0.807627828   0.542707847
C        0.956901991   0.245893003   0.340167231
C        0.043098009   0.754106997   0.659832769
H        0.022416710   0.153595990   0.313033710
H        0.977583290   0.846404010   0.686966290
C        0.771131988   0.269306261   0.255617666
C        0.228868012   0.730693739   0.744382334
C        0.652850645   0.378765293   0.282708985
C        0.347149355   0.621234707   0.717291015
C        0.462994923   0.392175655   0.192940332
C        0.537005077   0.607824345   0.807059668
C        0.403148927   0.302768506   0.084001267
C        0.596851073   0.697231494   0.915998733
H        0.259814627   0.314740185   0.016757517
H        0.740185373   0.685259815   0.983242483
C        0.525750373   0.196269824   0.058490144
C        0.474249627   0.803730176   0.941509856
H        0.478830729   0.128376775   0.971151210
H        0.521169271   0.871623225   0.028848790
C        0.705969389   0.179966480   0.142934709
C        0.294030611   0.820033520   0.857065291
H        0.804698818   0.098652977   0.124221693
H        0.195301182   0.901347023   0.875778307
C        0.184454672   0.523754793   0.135830920
C        0.815545328   0.476245207   0.864169080
H        0.287576875   0.544363666   0.053314825
H        0.712423125   0.455636334   0.946685175
H        0.118308380   0.611071476   0.178999457
H        0.881691620   0.388928524   0.821000543
H        0.013394359   0.440437861   0.110093147
H        0.986605641   0.559562139   0.889906853
N        0.053284394   0.319764373   0.444382321
N        0.946715606   0.680235627   0.555617679
O        0.705759527   0.466685324   0.381694456
O        0.294240473   0.533314676   0.618305544
O        0.356827705   0.498376849   0.225196110
O        0.643172295   0.501623151   0.774803890
S        0.766003561   0.110202377   0.587178900
S        0.233996439   0.889797623   0.412821100
Cu      -0.000000000   0.500000000   0.500000000

K_POINTS {automatic}
   3 3 3 0 0 0