[Pw_forum] bfgs optimization not going anywhere
Ilya Ryabinkin
igryabinkin at gmail.com
Tue Nov 24 20:03:12 CET 2015
Colleagues,
to summarize: what would be 'the best' DFT correction on to of
*existing* functionals, e.g. PBE for molecule-metal-interaction? As
far as I understood, vdw-DF must be used with the corresponding
pseudopotential (BTW, where one can get them?).
--
I.
On Tue, Nov 24, 2015 at 8:30 AM, Giuseppe Mattioli
<giuseppe.mattioli at ism.cnr.it> wrote:
>
> Dear Matej (and all)
>
>> As for DFT-D2, I admit I am a bit in the dark here. How 'wrong' is it? Or to
>> put differently, is it more wrong that not using dispersion correction at
>> all?
>
> Regarding the dispersion correction(s) this is the Stephan Grimme's paper which indicates that DFT-D2 doubles the DFT-D3 interaction energy between
> molecules and metal surfaces:
>
> J. Chem. Phys. (2010) 132, 154104
>
> In my experience of phthalocyanine/metal interactions (but if I remember well Ari has also performed calculations on porphyrin/phthalocyanine
> molecules adsorbed on metal surfaces and he can add his own knowledge), adsorption geometries and energies are very different, so that the results are
> also quite different. See for example this paper (Cu phthalocyanine interacting with Ag (100) with DFT-D2)
>
> PRL 105, 115702 (2010)
>
> And my paper (TiO phthalocyanine interacting with Ag (100) with vdW-DF)
>
> J. Phys. Chem. C 2014, 118, 5255
>
> And, yes, of course: if you use no dispersion correction you badly underestimate the interaction between the molecule and the surface...
>
> 2 more hints:
>
> 1) In the case of molecule/metal systems, ab initio functionals modeling long distance correlation between electrons should be (in my opinion)
> preferred to semiempirical functional with add pairwise forces based on tabulations (or partial calculations) of C6 coefficients. There is a nice
> perspective written by J. L. Bredas which addresses the issue
>
> Nature Nanotechnology
> 8,
> 230–231
> (2013)
>
> 2) Regarding lattice parameters, Ari is right in the case of vdwdf. But I've tried to simulate gold (bulk and) surfaces in contact with molecules by
> using the reparametrized vdwdf-c09 functional: lattice parameter of gold is ok, and also molecule-surface interactions are expected to be improved
> with respect to vdwdf!
>
>> Also, if I change/switch off the dispersion correction, then I will have to
>> re-optimize all already converged structures (metal, isolated molecules,
>> adsorbed intermediates), right? Looks rather tedious
>
> Yes, you should recalculate everything...:-(
>
> HTH
> Giuseppe
>
> On Tuesday, November 24, 2015 11:37:45 AM Matej Huš wrote:
>> Thanks for very useful comments.
>>
>> Yes, vacuum region is indeed too low in this example (whoops, seems like
>> I've attached an old input file). I also ran a calculation with 10 A of
>> vacuum without any improvement. Open shell is unnecessary as it quickly
>> converges to a closed shell solution. I've just wasted some CPU time with
>> that.
>>
>> Ectuwfc, ecutrhc are large enough (converged). I believe K points should
>> also not be the source of a problem.
>>
>> As for DFT-D2, I admit I am a bit in the dark here. How 'wrong' is it? Or to
>> put differently, is it more wrong that not using dispersion correction at
>> all? How about vdw-DF, how do I turn it on and does it perform better? Where
>> can I find more important about that?
>>
>> Also, if I change/switch off the dispersion correction, then I will have to
>> re-optimize all already converged structures (metal, isolated molecules,
>> adsorbed intermediates), right? Looks rather tedious
>>
>>
>> Matej
>>
>>
>>
>> -----Original Message-----
>> From: pw_forum-bounces at pwscf.org [mailto:pw_forum-bounces at pwscf.org] On
>> Behalf Of Ari P Seitsonen
>> Sent: Tuesday, November 24, 2015 11:22 AM
>> To: PWSCF Forum <pw_forum at pwscf.org>
>> Subject: Re: [Pw_forum] bfgs optimization not going anywhere
>>
>>
>> Dear Matej Hus,
>>
>> Adding to the previous comments (I think that it is ok to use the k
>> points, even though you might gain some CPU time by first indeed using
>> Gamma-only and then increasing, as your cell is quite large), have you
>> checked the length of your vacuum/lattice vector along the surface normal?
>> If I see correctly, you have only about six Ångströms, which is already very
>> (too) little, plus the DFT-D2 (Grimme-D2) adds quite strong an interaction
>> through the vacuum at such distances I believe, plus the dipole
>> correction...
>>
>> Greetings from Peaceful Montrouge/France,
>>
>> apsi
>>
>> PS My personal opinion of the vdW-DF* is, yes, they might be better, but
>> first check the literature about a "suitable empirical choice of the
>> particular mixture" of the functional, as some of the choices give quite
>> large lattice constants already (4-5 % larger than experimental, which, of
>> course, is not necessarily the target, rather a good adsorption geometry and
>> energy). And often the best agreement is found by tuning the exchange
>> functional, which naturally should have not nothing to do with the
>> vdW/London dispersion, which is pure correlation... So much about "ab
>> initio". ;) The good news of the day is that it seems that seldomly things
>> seem to go completely wrong, no matter which choice of the vdW-DF* you take,
>> but still, I would study a bit the literature first. If any one has a
>> reference for a good review on the vdW-DF* et co applied to surfaces and
>> adsorption, I would also be very thankful! :)
>>
>> -=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=
>> -
>> Ari Paavo Seitsonen / Ari.P.Seitsonen at iki.fi / http://www.iki.fi/~apsi/
>> Ecole Normale Supérieure (ENS), Département de Chimie, Paris
>> Mobile (F) : +33 789 37 24 25 (CH) : +41 79 71 90 935
>>
>> On Tue, 24 Nov 2015, Matej Huš wrote:
>> > Dear PW community
>> >
>> > I have a problem when trying to find optimized geometry of an adsorbed
>> > intermediate in "benzene" hydrogenation on Ru surface (see input below).
>> >
>> > I believe I am fairly close to optimised structure since I'm only
>> > adding one hydrogen atom to an already optimised reactant and only
>> > slight displacing the adjacent atoms.
>> >
>> >
>> >
>> > The problem is that BFGS doesn't seem to go anywhere. Energy only
>> > fluctuates, which to my understanding is a sign of being close to a
>>
>> minimum.
>>
>> > However, forces remain large.
>> >
>> >
>> >
>> > I've switched to the damp algorithm and the problem persists. I've
>> > searched through the forum and the usual approaches of tackling this
>> > issue do not seem to work.
>> >
>> >
>> >
>> > Any ideas? Thank you!
>> >
>> > Matej Hus
>> >
>> > Laboratory of Catalysis and Chemcial Reaction Engineering
>> >
>> > National Institute of Chemistry
>> >
>> > Ljubljana, Slovenia
>>
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> Giuseppe Mattioli
> CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
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--
*******************************************************
Ilya Ryabinkin
Postdoctoral Scholar
Physical and Environmental Sciences
University of Toronto Scarborough
http://www.utsc.utoronto.ca/~aizmaylov/Members.html
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