[Pw_forum] PWscf vs. CP

[Peter Winey]

Dear all,

I was doing an electronic minimization using the CPV code cp.x. To make sure
I did
not make mistakes, I also did a similar calculation using the PWscf code
pw.x.

Well, when I compared the results, I found quite some difference,
in particular,
the forces acting on atoms are quite different while the total energy are
close.

My question is whether I should expect to get same results from the two
codes?
If so, there must be something wrong with the input files that I used (see
below).

Thanks in advance for any suggestions that you may have!

-Peter

--------------------------pw.x input file---------
C2H4
 &control
    calculation='scf'
    restart_mode='from_scratch',
    wf_collect=.true.,
    prefix='pwscf',
    pseudo_dir = '/espresso-3.0/pseudo',
    outdir='.',
    tprnfor=.true.
 /
 &system
                       ibrav = 1
                   celldm(1) = 37.7945197733
    nat=6, ntyp=2,
    ecutwfc = 30.0,
    occupations='fixed',
 /
 &electrons
    conv_thr =  1.0d-8
    mixing_beta = 0.7
 /
ATOMIC_SPECIES
C   12.0107 C.pbe-van_ak.UPF
H   1.00794 H.pbe-van_ak.UPF
K_POINTS {gamma}
ATOMIC_POSITIONS {crystal}
C 0.46664509 0.5 0.5
C 0.53335491 0.5 0.5
H 0.43793698 0.5 0.45351762
H 0.56206302 0.5 0.45351762
H 0.56206302 0.5 0.54648238
H 0.43793698 0.5 0.54648238

--------------------------cp.x input file---------
 &control
    calculation='cp',
    restart_mode='from_scratch',
    ndr=52, ndw=53,
    nstep=400, iprint=10, isave=50,
    dt=5.0,
    etot_conv_thr  = 1.d-9,
    ekin_conv_thr  = 1.d-5,
    prefix = 'cp'
    pseudo_dir='/espresso-3.0/pseudo/',
    tprnfor = .TRUE.
    outdir='.',
 /
 &system
                       ibrav = 1
                   celldm(1) = 37.7945197733
    nat=6, ntyp=2,
    ecutwfc = 30.0,
 /
 &electrons
    electron_dynamics='damp'
 /
 &ions
    ion_dynamics='none',
 /
ATOMIC_SPECIES
C   12.0107 C.pbe-van_ak.UPF
H   1.00794 H.pbe-van_ak.UPF
ATOMIC_POSITIONS {crystal}
C 0.46664509 0.5 0.5
C 0.53335491 0.5 0.5
H 0.43793698 0.5 0.45351762
H 0.56206302 0.5 0.45351762
H 0.56206302 0.5 0.54648238
H 0.43793698 0.5 0.54648238
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