[Pw_forum] (no subject)

[Raghani Pushpa]

dear users,
i was doing the slab calculations and wanted to fix some of the middle
layers, so at the end of the atomic positions i gave "iforce(i=1-3)=0".
but in the output the warning comes as "Warning: card   IFORCE(I=1-4)=0
ignored". what does this warning mean? and is the code going to keep the
last three atoms fixed?

thanks,
pushpa

my input file is as follows:

 &control
    calculation='relax',
    restart_mode='from_scratch',
    tstress = .true.
    tprnfor = .true.
    prefix='ru',
    pseudo_dir = '../../pseudi/',
    outdir='./tmp/'
 /
 &system
    ibrav=  4, celldm(1) =5.0,  celldm(3) = 10.0527,
    nat=  6, ntyp= 2,
    ecutwfc =30.0,
    occupations='smearing', smearing='methfessel-paxton',
    degauss=0.002, nbnd=30,
 /
 &electrons
    conv_thr =  1.0d-10
    mixing_beta = 0.7
 /
 &ions
    upscale =10
 /
ATOMIC_SPECIES
 Ru 101.07 Ru.pbe-n-van.UPF
 Cu 63.55  Cu.pbe-d-rrkjus.UPF
ATOMIC_POSITIONS
Cu   0.0      0.0       2.09431
Cu   0.       0.577350 -2.09431
Ru   0.5      0.288675  1.25659
Ru   0.       0.577350  0.418863
Ru   0.       0.0      -0.418863
Ru   0.5      0.288675 -1.25659
  iforce(i=1-3)=0
K_POINTS {automatic}
 12 12 4 0 0 0