[Pw_forum] RE: Pw_forum digest, Vol 1 #456 - 2 msgs
Timothy A.V. Teatro
timtro at rogers.com
Thu Nov 18 18:13:21 CET 2004
Hi Aaron. Thank you very much for responding.
Yes, I have tried a more physically phesable distance. I initially had
it set at <0.25, 0.25, 0.25>, which I am assuming should also lead to
zero force, since the PBC's would create a 0k lattice right? So I'm
thinking great, now let's move it in slightly to perturb the system and
create some vibration. But no matter where I moved the second Si atom,
it didn't help.
I want to thank you again very much. I have attached the output file you
requested.
>From Aaron:
Hi Timothy,
Just some thoughts on your job... Have you tried a more physical
distance
between the two Si atoms? It can be very difficult to optimize the
electronic wavefunction when they are almost right on top of each other.
Also from what I understand, the procedure can be to fix the atoms,
optimize the electronic wavefunction (e-kinetic energy goes to
approximately zero) and then begin with moving the ions (in fact this
becomes more than one input file).
Finally if you can show your output we can more correctly diagnose your
problem(s).
I hope this helps,
Aaron
On Tue, 16 Nov 2004, Timothy A.V.
Teatro wrote:
> Hi. I'm really sorry to ask a question like this. I wrote this input
> file a while ago. I have been fiddling with it for a while now, and I
> can't figure out why I can't get two simple little silicon atoms to
> move! I am accustomed to using PWscf, but I am not trying to switch to
> FPMD for more accurate dynamics. But I cannot get any dynamics out of
> this thing! Even when I try putting the Si atoms very close to each
> other, where the forces should be enormous I can't get them to move.
>
> Thanks a lot for looking at this. I'm sure I did something very silly,
> which is going to embarrass me later.
>
> Here is a verbatim listing of the input script:
>
> #!/bin/sh
>
> PW_ROOT=$HOME/cpmd/FPMD
> PSEUDO=$HOME/cpmd/pseudo
> TMP_DIR=$HOME/cpmd/tmp0
>
> if [ ! -d results ]; then
> mkdir results
> fi
> cd results
>
> rm -rf $TMP_DIR/*
>
> cat > sih.cp1.in << EOF
>
> &CONTROL
> title = ' Silicon ',
> calculation = 'cp',
> restart_mode = 'from_scratch',
> pseudo_dir = '$PSEUDO/',
> outdir='$TMP_DIR/',
> ndr = 51,
> ndw = 51,
> nstep = 50,
> iprint = 10,
> isave = 100,
> tstress = .TRUE.,
> tprnfor = .TRUE.,
> dt = 5.0d0,
> etot_conv_thr = 1.d-9,
> ekin_conv_thr = 1.d-4,
> prefix = 'si'
> /
>
> &SYSTEM
> ibrav = 1,
> celldm = 10.61,
> nat = 2,
> ntyp = 1,
> nbnd = 4,
> nelec = 8,
> ecutwfc = 8.0,
> xc_type = 'BLYP'
> /
>
> &ELECTRONS
> emass = 400.d0,
> emass_cutoff = 2.5d0,
> orthogonalization = 'ortho',
> ortho_eps = 5.d-8,
> ortho_max = 15,
> electron_dynamics = 'sd',
> ! electron_damping = 0.3,
> electron_velocities = 'zero',
> electron_temperature = 'not_controlled',
> /
>
> &IONS
> ion_dynamics = 'verlet',
> ion_damping = 0.2,
> ion_radius(1) = 0.8d0,
> ion_radius(2) = 0.8d0,
> ion_velocities = 'zero',
> ion_temperature = 'nose',
> tempw = 1000,
> fnosep = 1.2,
> tolp=100,
> ion_nstepe = 10
> /
>
> &CELL
> cell_dynamics = 'pr',
> cell_velocities = 'zero',
> press = 0.0d0,
> /
>
> ATOMIC_SPECIES
> Si 28.086 Si.vbc.UPF 4
>
> ATOMIC_POSITIONS
> Si 0.00 0.00 0.00
> Si 0.00 0.00 0.10
>
> K_POINTS
> 1
> 0.0 0.0 0.0 1.0
> EOF
>
> $PW_ROOT/par2.x < sih.cp1.in > Si.md64H.out
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum
>
--__--__--
Message: 2
From: Paolo Giannozzi <giannozz at nest.sns.it>
Organization: Scuola Normale Superiore di Pisa
To: pw_forum at pwscf.org
Subject: Re: [Pw_forum] error in phonon calculation
Date: Wed, 17 Nov 2004 18:24:36 +0100
Reply-To: pw_forum at pwscf.org
On Wednesday 17 November 2004 13:34, Jose C. Conesa wrote:
> Concerning the answers by Stefano, Paolo and Eyvaz to my question:
>
> From Stefano:
> > The message you mention should come out when performing a
calculation
> > with lsda flag on and fixed occupation . is this your situation ?
>
> No. The system is indeed spin-polarized (nspin = 2,
> starting_magnetization(1) = 1) and uses lda, but I have
> "occupations = 'tetrahedra' "
are you sure? Phonon calculation in metals with the tetrahedron
method is not implemented: the code stops immediately if you try.
Only smearing is implemented.
> From Paolo:
> >actually this message shows up also in a spin-polarized calculation
> > with free occupations but no smearing or tetrahedron technique.
> > This case used to be forbidden in the self-consistent calculation,
> > but I think it is allowed now, so the message might be obsolete.
>
> Well, then: should I disregard the message, and rely on the
calculation
> (from this point of view) after all?
I am not sure, but it seems to me that in a spin-polarized system the
number of occupied bands might be incorrectly computed by the
phonon code in that particular case
Please do not post to pw_forum-admin at pwscf.org
Paolo
--
Paolo Giannozzi e-mail: giannozz at nest.sns.it
Scuola Normale Superiore Phone: +39/050-509876, Fax:-563513
Piazza dei Cavalieri 7 I-56126 Pisa, Italy
--__--__--
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