CCL:G: Gaussian IR frequency calculation

 Sent to CCL by: berger[a]chem.helsinki.fi
 Hello,
 300-400 cm-1 in the whole range also in my eyes seems much too large. Are
 you calculating the correct molecule? Is the experimental data correct?
 Are there impurities in the compound / solvens, ...? Is there a overall
 similarity between computed and experimental spectrum?
 Cheers
   B
 > 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 napisaÅ?(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: Víctor Luaña 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
 >>>> +--------------------------------------------+
 >>>> GroupPage : http://azufre.quimica.uniovi.es/  (being
 >>>> reworked)http://www.ccl.net/cgi-bin/ccl/send_ccl_messagehttp-:-//www.ccl.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 46202>
 >
 >