[Pw_forum] Problem: different output with identical input

[Paolo Giannozzi]

The differences you find are very small. Nothing to worry about in my
opinion.

By the way: Davidson diagonalization is typically faster than CG; do not
specify incompatible options in K_POINTS (gamma or automatic, not both;
gamma should be used unless you have a good reason not to)

Paolo
Il 28/dic/2016 01:46 PM, "Pablo García Risueño" <garcia.risueno at gmail.com>
ha scritto:
>
> 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  8.019670107
>
> ATOMIC_POSITIONS (angstrom)
> C  8.898432121  8.898432121  8.898432121
> C  9.783306562  9.783306562  8.019670109
>
>
> 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
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://pwscf.org/mailman/listinfo/pw_forum
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