From owner-chemistry@ccl.net Sat Mar 12 03:19:01 2011 From: "Lars Goerigk lars.goerigk-,-uni-muenster.de" To: CCL Subject: CCL: SSB-D functional and reaction barriers Message-Id: <-44117-110312031536-17388-Qx/8eilJSJNHhUaJwHX+eQ/./server.ccl.net> X-Original-From: Lars Goerigk Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=us-ascii Date: Sat, 12 Mar 2011 09:15:24 +0100 (CET) MIME-Version: 1.0 Sent to CCL by: Lars Goerigk [lars.goerigk^^uni-muenster.de] Dear Piotr, the SSB-D functional was (together with 46 other functionals and some MP2 variants) very recently benchmarked against a variety of problems dealing with thermochemistry, kinetics and noncovalent interactions: PCCP DOI: 10.1039/C0CP02984J http://pubs.rsc.org/en/Content/ArticleLanding/2011/CP/C0CP02984J Besides the popular Truhlar benchmark sets for barrier heights, also the barrier heights for pericyclic reactions were tested (BHPERI test set). If you can just afford a GGA functional for your calculation, then the findings showed that B97-D3 (that is Grimme's functional in combination with the new DFT-D3 correction) performs best for the barrier heights of these reactions. In general it was found that B97-D3 and revPBE-D3 are the most robust GGA functionals and are recommended for general GGA-applications. The DFT-D3 program can be downloaded from here: http://toc.uni-muenster.de/DFTD3/ In the PCCP paper mentioned above you will also find recommendations for higher rungs of Jacob's Ladder. In a nutshell, usage of a dispersion correction is crucial, also for reaction energies. If you use a hybrid, better and more robust alternatives than B3LYP are discussed (particularly for reaction energies B3LYP is the worst of 23 hybrids and on average not better than GGAs!). If possible, you could also apply a double-hybrid to your problem. I hope that this information could help you. Cheers, Lars Goerigk Piotr Nowak omenthegreat() gmail.com schrieb am 2011-03-12: > Dear all, > It has been shown that SSB-D functional gives excellent results for > Sn2 > reactions. This behavior is easy to explain because the functional > has been > optimized using energetics and barriers of those reactions. I haven't > found > any comprehensive benchmark including SSB-D, so here comes my > question: how > accurate is it for the barriers of other reactions? I am especially > interested in cycloaddition reactions (e.g. Diels-Alder, 1,3-dipolar, > etc.). > Does anyone have experience with this functional in these cases? Can > SSB-D > compete with other cutting-edge functionals like M05 and M06 > families? > Best regards, > Piotr Nowak > -- > Piotr Nowak > PhD student > University of Groningen > Stratingh Institute for Chemistry > Nijenborgh 4 > 9747 AG Groningen > The Netherlands > http://www.google.com/profiles/omenthegreat From owner-chemistry@ccl.net Sat Mar 12 04:59:00 2011 From: "Marcel Swart marcel.swart**icrea.cat" To: CCL Subject: CCL: SSB-D functional and reaction barriers Message-Id: <-44118-110312045150-26581-sXWv6zCFLUbBRLDabqUdVw#%#server.ccl.net> X-Original-From: Marcel Swart Content-Type: multipart/alternative; boundary=Apple-Mail-6--506216192 Date: Sat, 12 Mar 2011 10:52:10 +0100 Mime-Version: 1.0 (Apple Message framework v1082) Sent to CCL by: Marcel Swart [marcel.swart[*]icrea.cat] --Apple-Mail-6--506216192 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=iso-8859-1 Dear Piotr and Lars, note that the PCCP paper does not study SSB-D; instead of including Grimme's D2 correction, with which the SSB-D should be used, and for which all parameters were optimized, Lars and Grimme used the D3 correction. I can understand this, because the D3 correction is reportedly much better than D2. But the energies of "SSB" or "SSB-D3" do say nothing about SSB-D. SSB-D was found to be the best GGA for E2 and Sn2 reactions=20 of X- + CH3CH2X: J. Chem. Theory Comput. 2010, 6, 3145-3152. Note that SSB is a separate functional, already described in the 2009 paper of SSB-D (JCP 2009, 131, 094103), and with parameters that are different from SSB-D. Most importantly, SSB does not contain any of Grimme's dispersion corrections. Marcel On 12 Mar 2011, at 09:15, Lars Goerigk lars.goerigk-,-uni-muenster.de = wrote: >=20 > Sent to CCL by: Lars Goerigk [lars.goerigk^^uni-muenster.de] > Dear Piotr, >=20 > the SSB-D functional was (together with 46 other functionals and some = MP2 > variants) very recently benchmarked against a variety of problems = dealing with > thermochemistry, kinetics and noncovalent interactions: > PCCP DOI: 10.1039/C0CP02984J > http://pubs.rsc.org/en/Content/ArticleLanding/2011/CP/C0CP02984J >=20 > Besides the popular Truhlar benchmark sets for barrier heights, also = the > barrier heights for pericyclic reactions were tested (BHPERI test = set). If you > can just afford a GGA functional for your calculation, then the = findings > showed that B97-D3 (that is Grimme's functional in combination with = the new > DFT-D3 correction) performs best for the barrier heights of these = reactions. > In general it was found that B97-D3 and revPBE-D3 are the most robust = GGA > functionals and are recommended for general GGA-applications. >=20 > The DFT-D3 program can be downloaded from here: >=20 > http://toc.uni-muenster.de/DFTD3/ >=20 > In the PCCP paper mentioned above you will also find recommendations = for > higher rungs of Jacob's Ladder. > In a nutshell, usage of a dispersion correction is crucial, also for = reaction > energies. > If you use a hybrid, better and more robust alternatives than B3LYP = are > discussed (particularly for reaction energies B3LYP is the worst of 23 = hybrids > and on average not better than GGAs!). > If possible, you could also apply a double-hybrid to your problem. >=20 > I hope that this information could help you. >=20 > Cheers, > Lars Goerigk >=20 >=20 > Piotr Nowak omenthegreat() gmail.com schrieb am 2011-03-12: >> Dear all, >=20 >> It has been shown that SSB-D functional gives excellent results for >> Sn2 >> reactions. This behavior is easy to explain because the functional >> has been >> optimized using energetics and barriers of those reactions. I haven't >> found >> any comprehensive benchmark including SSB-D, so here comes my >> question: how >> accurate is it for the barriers of other reactions? I am especially >> interested in cycloaddition reactions (e.g. Diels-Alder, 1,3-dipolar, >> etc.). >> Does anyone have experience with this functional in these cases? Can >> SSB-D >> compete with other cutting-edge functionals like M05 and M06 >> families? >=20 >> Best regards, >> Piotr Nowak =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D dr. Marcel Swart ICREA Research Professor at Institut de Qu=EDmica Computacional Universitat de Girona Facultat de Ci=E8ncies Campus Montilivi 17071 Girona Catalunya (Spain) tel +34-972-418861 fax +34-972-418356 e-mail marcel.swart(_)icrea.cat marcel.swart(_)udg.edu web http://www.marcelswart.eu =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D --Apple-Mail-6--506216192 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=iso-8859-1 Dear = Piotr and Lars,

note that the PCCP paper does not = study SSB-D;
instead of including Grimme's D2 correction, = with
which the SSB-D should be used, and for = which all
parameters were optimized, Lars and = Grimme used
the D3 correction. I can understand this, because = the
D3 correction is reportedly much better than = D2.

But the energies of "SSB" or "SSB-D3" do = say nothing about SSB-D.
SSB-D was found to be the best GGA = for E2 and Sn2 reactions 
of X- + CH3CH2X: J. = Chem. Theory Comput. 2010, 6, = 3145-3152.

Note that SSB is a separate = functional, already described
in the 2009 paper of SSB-D (JCP = 2009, 131, 094103),
and with parameters that are different = > from SSB-D.
Most importantly, SSB does not contain any of = Grimme's
dispersion = corrections.

Marcel

On 12 Mar 2011, at 09:15, Lars Goerigk lars.goerigk-,-uni-muenster.de wrote:


Sent to CCL by: Lars Goerigk = [lars.goerigk^^uni-muenster.de]
Dear Piotr,

the SSB-D = functional was (together with 46 other functionals and some = MP2
variants) very recently benchmarked against a variety of problems = dealing with
thermochemistry, kinetics and noncovalent = interactions:
PCCP DOI:  10.1039/C0CP02984J
= http://pubs.rsc.org/en/Content/ArticleLanding/2011/CP/C0CP02984J
Besides the popular Truhlar benchmark sets for barrier heights, also = the
barrier heights for pericyclic reactions were tested (BHPERI test = set). If you
can just afford a GGA functional for your calculation, = then the findings
showed that B97-D3 (that is Grimme's functional in = combination with the new
DFT-D3 correction) performs best for the = barrier heights of these reactions.
In general it was found that = B97-D3 and revPBE-D3 are the most robust GGA
functionals and are = recommended for general GGA-applications.

The DFT-D3 program can = be downloaded from = here:

http://toc.uni-muenster.de/DFTD3/

In the PCCP paper = mentioned above you will also find recommendations for
higher rungs = of Jacob's Ladder.
In a nutshell, usage of a dispersion correction is = crucial, also for reaction
energies.
If you use a hybrid, better = and more robust alternatives than B3LYP are
discussed (particularly = for reaction energies B3LYP is the worst of 23 hybrids
and on average = not better than GGAs!).
If possible, you could also apply a = double-hybrid to your problem.

I hope that this information could = help you.

Cheers,
Lars Goerigk


Piotr Nowak = omenthegreat() gmail.com schrieb am 2011-03-12:
Dear all,

It = has been shown that SSB-D functional gives excellent results = for
Sn2
reactions. = This behavior is easy to explain because the = functional
has = been
optimized using = energetics and barriers of those reactions. I = haven't
found
any = comprehensive benchmark including SSB-D, so here comes = my
question: = how
accurate is it for the = barriers of other reactions? I am especially
interested in cycloaddition reactions (e.g. Diels-Alder, = 1,3-dipolar,
etc.).
Does = anyone have experience with this functional in these cases? = Can
SSB-D
compete = with other cutting-edge functionals like M05 and = M06
families?

Best= regards,
Piotr = Nowak

=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

Institut de Qu=EDmica = Computacional
Universitat de Girona

Facultat de Ci=E8ncies
Campus = Montilivi
17071 Girona
Catalunya = (Spain)

tel
+34-972-418861
fax
+34-972-418356
e-mailmarcel.swart(_)udg.edu




= --Apple-Mail-6--506216192-- From owner-chemistry@ccl.net Sat Mar 12 12:10:00 2011 From: "Kavitha velappan kavitha.velappan(a)gmail.com" To: CCL Subject: CCL: NHC-structure optimization! Message-Id: <-44119-110312120638-21824-43h8eXmuNQNdqi/yCtRj2g=-=server.ccl.net> X-Original-From: Kavitha velappan Content-Type: multipart/alternative; boundary=0015174be4d09c8686049e4c198d Date: Sat, 12 Mar 2011 22:36:31 +0530 MIME-Version: 1.0 Sent to CCL by: Kavitha velappan [kavitha.velappan|,|gmail.com] --0015174be4d09c8686049e4c198d Content-Type: text/plain; charset=ISO-8859-1 Dear CCL subscribers, I tried to optimize the structure of N-heterocyclic carbene at the B3LYP/6-311++G** level. The optimized structure correspond to that of sp3 hybridized carbene(!!!) - obtained by NBO analysis. The lone pair of electron on carbene carbon delocalized into the antibonding orbital of the adjacent N-C bond. Is there a way to get the structure corresponding to sp2 hybridized carbene (avoiding the possibility of delocalization)? Whether optimization using a larger basis set/other methods will solve this? Any help would be greatly appreciated. Kavitha --0015174be4d09c8686049e4c198d Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Dear CCL subscribers,

I tried to optimize the structure of N-heteroc= yclic carbene at the B3LYP/6-311++G** level. The optimized structure corres= pond to that of sp3 hybridized carbene(!!!) - obtained by NBO analysis. The= lone pair of electron on carbene carbon delocalized into the antibonding o= rbital of the adjacent N-C bond. Is there a way to get the structure corres= ponding to sp2 hybridized carbene (avoiding the possibility of delocalizati= on)? Whether optimization using a larger basis set/other methods will solve= this?

Any help would be greatly appreciated.
Kavitha
--0015174be4d09c8686049e4c198d--