CCL:G: Gaussian IR frequency calculation
- From: "Abrash, Samuel"
<sabrash]=[richmond.edu>
- Subject: CCL:G: Gaussian IR frequency calculation
- Date: Tue, 24 Mar 2015 17:03:10 +0000
Sent to CCL by: "Abrash, Samuel" [sabrash ~~ richmond.edu]
So I think the data that Robert just cited supports my claim of a 3% error. In
the range 4000 cm-1 to 400 cm-1, the mid-ir, a 3% error would range from 120
cm-1 to 12 cm-1 so a 31 cm-1 average seems to be a bit below 3%. The other
support for my claim is to go to the CCCDB (I think that's the correct number of
C's) hosted at NIST, and check out the correction factors. For the types of
high quality functional/basis set combinations, the correction factors are
greater than .97, again consistent with an error of ~3%.
Samuel A. Abrash
Associate Professor, Department of Chemistry
Coordinator, Environmental Studies Program
University of Richmond
sabrash**richmond.edu
Cell: (804) 363-2597
www.richmond.edu/~sabrash
“At the time God created the world and desired to reveal the depth of His
being from out of the hidden, the light came from darkness and they were joined
together. Because of this, out of darkness came the light, and out of the
hidden came the revealed and out of the good came evil and out of mercy came
severe judgement, and everything is intertwined with everything else… the
good inclination and the evil inclination, the right and the left.” The
Zohar
-----Original Message-----
> From: owner-chemistry+sabrash==richmond.edu**ccl.net [mailto:owner-chemistry+sabrash==richmond.edu**ccl.net] On Behalf Of Robert
Molt r.molt.chemical.physics ~ gmail.com
Sent: Monday, March 23, 2015 10:58 PM
To: Abrash, Samuel
Subject: CCL:G: Gaussian IR frequency calculation
Sent to CCL by: Robert Molt [r.molt.chemical.physics]![gmail.com]
I respectfully disagree with the claim that KS-DFT functionals get 97% accuracy
of the correct value, and the remaining 3% is mostly anharmonic. That assumes
that KS-DFT functionals are describing electron correlation perfectly, as
opposed to it being an approximate method varying in semi-empirical character
from none to high.
The mean absolute error over the G2 set of vibrational frequencies of B3LYP is
31 wavenumbers (see the 1998 paper from Adamo and Barone), obviously weighted
more heavily for the higher values frequencies statistically. The RMS error can
be as high as 42 wavenumbers (1993 Pople paper).
The first harmonic mode of many molecules is often small, and the percent error
is much higher on this first mode (independent of harmonic vs. anharmonic).
On 3/23/15 8:51 PM, Abrash, Samuel sabrash%a%richmond.edu wrote:
> Sent to CCL by: "Abrash, Samuel" [sabrash|a|richmond.edu] With an
> appropriate functional with a good basis set, dft should get you to within
about 97% of the correct value. The remainder of the error will be due to the
harmonic approximation. Adding an anharmonic correction can get you to within
99%.
>
> Sent from my iPhone
>
>> On Mar 23, 2015, at 8:45 PM, zborowsk zborowsk^chemia.uj.edu.pl
<owner-chemistry.:.ccl.net> wrote:
>>
>>
>> Sent to CCL by: zborowsk [zborowsk^chemia.uj.edu.pl] W dniu
>> 2015-03-23 19:26, ggotelli()kaliumtech.com napisał(a):
>>> Sent to CCL by: [ggotelli[]kaliumtech.com] Thank you all for your
>>> help!
>>> I'll condense all my notes in the same mail.
>>>
>>> Krzysztof , yes I observed the difference in the whole spectrum.
>> Well, something strange. 300-400 cm-1 difference between theory and
experiment around 3000 cm-1 and also around 100 cm-1?? By the way, do you have
positive or negative (imaginary) frequencies around 100???
>>
>>
>>> Serdar, the molecule that I 'm trying to calculate and where I have
>>> the differences is a dimer derived from dilactide. To estimate a
>>> scaling factor my reference molecule is dilactide in itself, which
>>> in turn has little differences between the calculated spectrum and
>>> the real one, depending on the peaks.
>>>
>>> André, thanks for the scaling factor reference.
>>>
>>> Stent, the polymer spectrum was made with an ATR device and without
solvent.
>>> Because of this all calculations have done in vacuum.
>>>
>>> Robert, thanks for all your comments, they made me realize that my
>>> error was trying to adjust a dimer spectrum to a polymer spectrum,
>>> what are, of course, very different things. Although the dimer
peaks
>>> are displaced with respect to those of the polymer, it can be seen
>>> from the GView animation that they correspond to what is expected,
beyond the displacement involved.
>>>
>>> Regards!
>>> Gustavo Gotelli
>>> Polymer Synthesis
>>> Pharmaceutical Technology Department Faculty of Pharmacy and
>>> Biochemistry Buenos Aires University Argentina
>>>
>>> -----Mensaje original-----
>>> De: owner-chemistry+ggotelli==kaliumtech.com a ccl.net
>>> [mailto:owner-chemistry+ggotelli==kaliumtech.com a ccl.net] En
>>> nombre de Víctor Luaña Cabal
victor^^fluor.quimica.uniovi.es Enviado
>>> el: sábado, 21 de marzo de 2015 21:16
>>> Para: Gotelli, Gustavo A
>>> Asunto: CCL: Gaussian IR frequency calculation
>>>
>>>
>>> Sent to CCL by: =?iso-8859-1?Q?V=EDctor_Lua=F1a?= Cabal
>>> [victor]|[fluor.quimica.uniovi.es]
>>> On Sat, Mar 21, 2015 at 05:56:44PM -0400, Robert Molt
>>> r.molt.chemical.physics],[gmail.com wrote:
>>>> Sent to CCL by: Robert Molt
[r.molt.chemical.physics---gmail.com]
>>>> Moreover, you are using the B3LYP functional. It has limited
>>>> accuracy, depending on the system specifics. If it is a
>>>> multi-reference problem, great care is necessary.
>>>>
>>>> Also note that you can only compare the TOTAL spectrum, not any
one peak.
>>> Robert,
>>>
>>> 1) Let me take your highly correct advise to remember to the newest
>>> generations that the role on computational chemistry is not
being
>>> able to reproduce the number of the experiment.
>>>
>>> 2) The experiment helps in modulating our calculations, and the
final
>>> objective is a perfect reprodution of the experiment.
>>>
>>> 3) But the reason is not substituting experiments. The reason is
that
>>> in the processs of mimicking it we learn the rules that govern
>>> Nature.
>>>
>>> 4) There are too many questions in this forum that tend to ignore
>>> this rule and it is important to remember it again and again.
>>>
>>> Best regards,
>>> Dr. Víctor Luaña
>>> --
>>> . . "The hardest part in solving a problem is
recognizing
>>> / `' \ its existence. Learning the causes CAN be the road to
>>> /(o)(o)\ the solution."
>>> /`. \/ .'\ -- ¿?
>>> / '`'` \ "Lo mediocre es peor que lo bueno, pero
también es peor
>>> | \'`'`/ | que lo malo, porque la mediocridad no es un grado, es
>>> |una | '`'`| | actitud"
>>> \/`'`'`'\/ -- Jorge Wasenberg, 2015
>>>
===(((==)))==================================+=========================
>>> ! Dr.Víctor Luaña ! Mediocre
is worse than
>>> ! Departamento de Química Física y Analítica ! good,
but it is also !
>>> Universidad de Oviedo, 33006-Oviedo, Spain ! worse than bad,
because
>>> ! e-mail: victor-#-fluor.quimica.uniovi.es ! mediocrity is not
a grade,
>>> ! phone: +34-985-103491 fax: +34-985-103125 ! it is an attitude
>>> +--------------------------------------------+
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>>> cl.net/chemistry/sub_unsub.shtmlhttp://www.ccl.net/spammers.txt--
>> https://www.youtube.com/watch?v=IGyfx3Pmeyk
>> Krzysztof K. Zborowski
>> Faculty of Chemistry
>> Jagiellonian University
>> 3 Ingardena Street
>> 30-060 Krakow
>> Poland
>> phone: +48(12)663-2067
>> email: zborowsk(~)chemia.uj.edu.pl
>> gg 3817259
>> skype kzys70
>> www.chemia.uj.edu.pl/~zborowskhttp://www.ccl.net/chemistry/sub_unsub.
>> shtml>
>
--
Dr. Robert Molt Jr.
r.molt.chemical.physics=-=gmail.com
Nigel Richards Research Group
Department of Chemistry & Chemical Biology Indiana University-Purdue
University Indianapolis LD 326
402 N. Blackford St.
Indianapolis, IN 46202http://www.ccl.net/cgi-bin/ccl/send_ccl_messagehttp-:-//www.ccl.net/chemistry/sub_unsub.shtmlhttp-:-//www.ccl.net/spammers.txt