[Pw_forum] Problem: different output with identical input

Paolo Giannozzi p.giannozzi at gmail.com
Wed Dec 28 14:32:59 CET 2016


If the quantity you are trying to compute is sensitive to differences of
the order of 4*10^{-5} A in atomic positions, you have chosen an hopeless
task, in my opinion.

Paolo

Il 28/dic/2016 02:18 PM, "Pablo García Risueño" <garcia.risueno at gmail.com>
ha scritto:

> Dear professor
>
> Thank you very much for your reply. The differences are important in this
> case, my final calculated quantities are very sensitive to these optimized
> positions. Should I change any of the ***conv_thr variables, or other
> variable, to have the same result for same inputs?
>
> Is there any random number in the algorithm of relax calculations, can we
> be sure that different outputs with the same input are not due to any bug?
>
> Thank you very much. Best regards.
>
> 2016-12-28 14:10 GMT+01:00 Paolo Giannozzi <p.giannozzi at gmail.com>:
>
>> 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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>>
>
>
>
> --
> --
>
> 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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