[QE-users] r vectors and dispersion correction

[Michalchuk, Adam]

Hello,

I am running qe-6.7 and running frequently into the error 'too many r-vectors' during calculation=relax. I am able to bypass this error by turning off the DFT-D2 vdw correction. Unfortunately, I do need dispersion correction for my system (a molecular crystal) so cannot afford to eliminate this correction.

    Error in routine rgen (18496):
     too many r-vectors

Is there another way around this error?

I have verified that the structure is fine - the unit cell and interatomic distances are all very reasonable. I noticed Prof Giannozzi once suggested
> increase the value of mxr in PW/src/ewald.f90, PW/src/force_ew.f90,
> PW/src/stres_ewa.f90, recompile

However before modifying the code (default mxr = 50 ) wanted to verify to what extent such modifications are 'safe', or if there is a better way to solve this problem.


For reference, my input file is

&CONTROL
prefix='test1'
calculation ='relax'
wf_collect=.true.
nstep=1000
tstress=.true.
tprnfor=.true.
outdir='./scratch'
pseudo_dir = '/home/QE/pseudopotentials/'
etot_conv_thr=1.0d-9
forc_conv_thr=1.0d-4
/

&SYSTEM
  ibrav = 6
  celldm(1) = 26.6779799
  celldm(3) = 0.2653546
  nat = 50
  ntyp = 5
  input_dft = 'pbe'
  !!vdw_corr = 'dft-d'
  ecutwfc = 80
  ecutrho = 800
/

&ELECTRONS
electron_maxstep = 1000
conv_thr = 1.0d-10
/

&IONS
ion_dynamics='bfgs'
/

&CELL
cell_dynamics = 'bfgs'
/

K_POINTS automatic
2 2 4 0 0 0

ATOMIC_SPECIES
   H    1.00750   H.pbe-kjpaw_psl.1.0.0.UPF
   N   14.00650   N.pbe-n-kjpaw_psl.1.0.0.UPF
  Cl   35.45150  Cl.pbe-n-kjpaw_psl.1.0.0.UPF
   C   12.01060   C.pbe-n-kjpaw_psl.1.0.0.UPF
 Cd  112.41100  Cd.pbe-n-kjpaw_psl.1.0.0.UPF

Many thanks in advance,

Adam Michalchuk
Federal Institute for Materials Research and Testing, Germany
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