[Pw_forum] Problem: different output with identical input

[Pablo García Risueño]

Dear Espresso community

I have one problem that is important for me; it is somewhat surprising. I
run geometry optimization (relax) calculations with pw.x with identical
input files, and I obtain rather different final coordinates. The problem
does not happen if ecutwfc is 30, but it does appear for cutoffs of 60, 80
or 90. Below one can see the exact input file, and examples of the
difference between the final coordinates for both runs (both run with
identical input) for given cutoffs.

Could anybody give me a clue on the origin of the problem, and how to solve
it?

Thank you very much. Best regards.



Input file:



&CONTROL

    calculation = 'relax',

    restart_mode = 'from_scratch',

    prefix='',

    outdir = './',

    pseudo_dir = '/path_xxx/PP/',

    forc_conv_thr = 1.0D-6 ,

    etot_conv_thr = 1.0D-8 ,

 /

&system

    ibrav = 0, a=18.0,

    nat= 26, ntyp= 2,

    ecutwfc = 30d0,

    nbnd = 100,

/

&electrons

    conv_thr = 1.0e-9,

    mixing_beta = 0.7,

    mixing_mode = 'plain',

    diagonalization = 'cg'

/

&IONS

/



ATOMIC_SPECIES

C   12.0107   C.pz-vbc.UPF

H   1.007825035  H.pz-vbc.UPF



ATOMIC_POSITIONS { angstrom }

C  8.891700e+00     8.891700e+00     8.891700e+00

C  9.783400e+00     9.783400e+00     8.000000e+00

C  9.783400e+00     8.000000e+00     9.783400e+00

C  8.000000e+00     9.783400e+00     9.783400e+00

C  8.891700e+00     1.067510e+01     1.067510e+01

C  1.067510e+01     1.067510e+01     8.891700e+00

C  1.067510e+01     8.891700e+00     1.067510e+01

C  9.783400e+00     1.156680e+01     9.783400e+00

C  9.783400e+00     9.783400e+00     1.156680e+01

C  1.156680e+01     9.783400e+00     9.783400e+00

H  8.391700e+00     8.391700e+00     8.391700e+00

H  7.500000e+00     1.028340e+01     9.283400e+00

H  7.500000e+00     9.283400e+00     1.028340e+01

H  9.283400e+00     1.028340e+01     7.500000e+00

H  1.028340e+01     9.283400e+00     7.500000e+00

H  9.283400e+00     7.500000e+00     1.028340e+01

H  1.028340e+01     7.500000e+00     9.283400e+00

H  9.283400e+00     1.206680e+01     9.283400e+00

H  1.206680e+01     9.283400e+00     9.283400e+00

H  9.283400e+00     9.283400e+00     1.206680e+01

H  8.391700e+00     1.117510e+01     1.117510e+01

H  1.117510e+01     1.117510e+01     8.391700e+00

H  1.117510e+01     8.391700e+00     1.117510e+01

H  1.028340e+01     1.206680e+01     1.028340e+01

H  1.028340e+01     1.028340e+01     1.206680e+01

H  1.206680e+01     1.028340e+01     1.028340e+01





CELL_PARAMETERS {cubic}

 1.00  0.00  0.00

 0.00  1.00  0.00

 0.00  0.00  1.00



K_POINTS {gamma} {automatic}

1 1 1  0 0 0





The program is run with



mpirun -np 32 /path_xxx/pw.x


Final coordinates: The first two rows for ecutwfc=30 for two runs with
identical input are:

ATOMIC_POSITIONS (angstrom)
C  8.898432121  8.898432121  8.898432121
C  9.783306562  9.783306562  8.01967010*7*

ATOMIC_POSITIONS (angstrom)
C  8.898432121  8.898432121  8.898432121
C  9.783306562  9.783306562  8.01967010*9*


Final coordinates: The first two rows for ecutwfc=60 for two runs with
identical input are:

ATOMIC_POSITIONS (angstrom)
C  8.904988579  8.904988579  8.904988579
C  9.783426086  9.783426086  8.031809869

ATOMIC_POSITIONS (angstrom)
C  8.904962246  8.904962246  8.904962246
C  9.783425401  9.783425401  8.031847251

-- 
--

Dr. Pablo García Risueño

Institut für Physikalische Chemie, Universität Hamburg, Grindelallee 117,
20146 Hamburg

Tel. +49 040 42 83 84 82 7
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