CCL: Separation of steric and electronic effects
- From: Sebastian Kozuch <kozuchs(a)yahoo.com>
- Subject: CCL: Separation of steric and electronic effects
- Date: Wed, 10 Nov 2010 13:28:05 -0800 (PST)
B3LYP models electronic and repulsivesteric effects quite well (although I
would
go for some other functional when having transition metals). But as most of the
DFT methods, it does not work well with dispersive forces. If you add a
dispersion correction add on (for instance check:
http://jcp.aip.org/resource/1/jcpsa6/v132/i15/p154104_s1 )
the results will be
much better (look at
http://pubs.rsc.org/en/Content/ArticleLanding/2010/DT/C0DT00778A
). But, if you
work with a QM/MM type of method, do not add dispersion forces. You should
choose an outer layer that can manage dispersion forces by itself, (like an MM
method).
MP2 may be OK, but not advisable with transition metals. You can forget CCSD,
unless you have a quantum computer.
Now, one of the biggest problem with the separation of steric and electronic
effects is that you will loose accuracy everywhere, and you will have to work
with qualitative values. One of the problems will be the solvation model, that
does not work with ONIOM (unless there is some update I am not aware off). And
you will have lots of artifacts from the separation scheme.
You may want to have a look at J. Mol. Cat. A 2010 , 324 , 120-126. In
there we tried to tackle some of those problems.
Best,
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
..........Sebastian Kozuch...........
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
....Weizmann Institute of Science....
...........Rehovot, Israel...........
.. sebastian.kozuch#,#weizmann.ac.il ..
http://yfaat.ch.huji.ac.il/kozuch.htm
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
________________________________
> From: Michael Dimitrov mich.dimitrov^^gmail.com
<owner-chemistry#,#ccl.net>
To: "Kozuch, Sebastian " <kozuchs#,#yahoo.com>
Sent: Wed, November 10, 2010 9:08:22 PM
Subject: CCL: Separation of steric and electronic effects
Sent to CCL by: Michael Dimitrov [mich.dimitrov,+,gmail.com]
Hi,
I am interested in the procedure of computational separation of steric
and electronic effects as described in Scheme 3 of the article Eur. J.
Inorg. Chem. 2007, 5390 ( http://dx.doi.org/10.1002/ejic.200700850 )
I doubt if B3LYP level is good enough to take into account steric and
electronic factors? Perhaps it would be better to use MP2, CCSD or
another density functional for accurate description of both steric and
electronic factors?
Best regards,
Michael Dimitrov.http://www.ccl.net/cgi-bin/ccl/send_ccl_messagehttp-:-//www.ccl.net/chemistry/sub_unsub.shtmlhttp-:-//www.ccl.net/spammers.txt--0-1455235642-1289424485=:365
Content-Type: text/html; charset=us-ascii
<html><head><style type="text/css"><!-- DIV
{margin:0px;} --></style></head><body><div
style="font-family:arial,helvetica,sans-serif;font-size:10pt">B3LYP
models electronic and <span style="font-style:
italic;">repulsive</span><span> steric effects quite well
(although I would go for some other functional when having transition metals).
But as most of the DFT methods, it does not work well with dispersive forces. If
you add a dispersion correction add on (for instance check: <a
target="_blank" href="http://jcp.aip.org/resource/1/jcpsa6/v132/i15/p154104_s1";>http://jcp.aip.org/resource/1/jcpsa6/v132/i15/p154104_s1</a> ) the
results will be much better (look at <a target="_blank"
href="http://pubs.rsc.org/en/Content/ArticleLanding/2010/DT/C0DT00778A";>http://pubs.rsc.org/en/Content/ArticleLanding/2010/DT/C0DT00778A</a>
). But, if you work with a QM/MM type of method, do not add dispersion forces.
You should choose an outer layer that can manage dispersion
forces by itself, (like an MM</span> method).<br>MP2 may be OK, but
not advisable with transition metals. You can forget CCSD, unless you have a
quantum computer.<br>Now, one of the biggest problem with the separation
of steric and electronic effects is that you will loose accuracy everywhere, and
you will have to work with qualitative values. One of the problems will be the
solvation model, that does not work with ONIOM (unless there is some update I am
not aware off). And you will have lots of artifacts from the separation
scheme.<br>You may want to have a look at <font
face="Helvetica,Arial,sans-serif"><i>J. Mol. Cat. A
</i>
<b>
2010
</b>,
<i>
324
</i>,
120-126. In there we tried to tackle some of those
problems.<br><br>Best,<br></font><div> </div><span
style="font-family:
courier,monaco,monospace,sans-serif;">xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx</span><br
style="font-family: courier,monaco,monospace,sans-serif;"><span
style="font-family:
courier,monaco,monospace,sans-serif;">..........Sebastian
Kozuch...........</span><br style="font-family:
courier,monaco,monospace,sans-serif;"><span style="font-family:
courier,monaco,monospace,sans-serif;">xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx</span><br
style="font-family: courier,monaco,monospace,sans-serif;"><span
style="font-family:
courier,monaco,monospace,sans-serif;">....Weizmann Institute of
Science....</span><br style="font-family:
courier,monaco,monospace,sans-serif;"><span style="font-family:
courier,monaco,monospace,sans-serif;">...........</span><span
style="font-family: courier,monaco,monospace,sans-serif;">Rehovot,
Israel...........</span><br
style="font-family: courier,monaco,monospace,sans-serif;"><span
style="font-family: courier,monaco,monospace,sans-serif;">..
sebastian.kozuch#,#weizmann.ac.il ..</span><br style="font-family:
courier,monaco,monospace,sans-serif;"><a rel="nofollow"
target="_blank" href="http://yfaat.ch.huji.ac.il/kozuch.htm";><span
style="font-family: courier,monaco,monospace,sans-serif;">http://yfaat.ch.huji.ac.il/kozuch.htm</span></a><br
style="font-family: courier,monaco,monospace,sans-serif;"><span
style="font-family:
courier,monaco,monospace,sans-serif;">xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx</span><div><br></div><div
style="font-family: arial,helvetica,sans-serif; font-size:
10pt;"><br><div style="font-family:
arial,helvetica,sans-serif; font-size: 10pt;"><font
face="Tahoma" size="2"><hr
size="1"><b><span style="font-weight:
bold;">From:</span></b> Michael Dimitrov
mich.dimitrov^^gmail.com
<owner-chemistry#,#ccl.net><br><b><span
style="font-weight:
bold;">To:</span></b> "Kozuch, Sebastian "
<kozuchs#,#yahoo.com><br><b><span
style="font-weight: bold;">Sent:</span></b> Wed,
November 10, 2010 9:08:22 PM<br><b><span style="font-weight:
bold;">Subject:</span></b> CCL: Separation of steric and
electronic effects<br></font><br><br>Sent to CCL by:
Michael Dimitrov [mich.dimitrov,+,gmail.com]<br>Hi,<br><br>I
am interested in the procedure of computational separation of
steric<br>and electronic effects as described in Scheme 3 of the article
Eur. J.<br>Inorg. Chem. 2007, 5390 ( <a href="http://dx.doi.org/10.1002/ejic.200700850";
target="_blank">http://dx.doi.org/10.1002/ejic.200700850</a> )<br><br>I
doubt if B3LYP level is good enough to take into account steric
and<br>electronic factors? Perhaps it would be better to use MP2, CCSD
or<br>another density functional for accurate description of both steric
and<br>electronic factors?<br><br>Best
regards,<br>Michael
Dimitrov.<br><br><br><br<br<br<br<br><br>E-mail
to subscribers: <a ymailto="mailto:CHEMISTRY#,#ccl.net"; href="mailto:CHEMISTRY#,#ccl.net";>CHEMISTRY#,#ccl.net</a> or
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