From owner-chemistry@ccl.net Mon Jun 2 08:00:00 2014 From: "Laidig, Bill laidig.wd(_)pg.com" To: CCL Subject: CCL: DFT14poll Message-Id: <-50136-140601204631-21199-G1enabkfcY1aW/o2GzE/SQ_+_server.ccl.net> X-Original-From: "Laidig, Bill" Content-Language: en-US Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset="utf-8" Date: Mon, 2 Jun 2014 00:45:27 +0000 MIME-Version: 1.0 Sent to CCL by: "Laidig, Bill" [laidig.wd=pg.com] I strongly disagree with this position. There are many scientifically valid reasons to know which functionals are most popular among theoretical and computational chemists (who, I am assuming, are the bulk of this mailing list). For example: 1. Even if a functional is clearly inferior to another, if it is used much more in real calculations then there may be several reasons to use the inferior function: a. It is likely more widely implemented meaning you have a wider choice of programs to use and ways to validate that the calculations were performed correctly. b. Wider use means that there is a larger statistical pool of data for assessing accuracy, etc. This is often much more important than using a marginally better method. We see this in the long-term popularity of methods such as HF/3-21G, and B3LYP/6-31G*. 2. Highly accurate, but arcane theoretical methods make communication of results difficult outside the expert community as the reader has little basis for assessing the quality of results. I learned this the hard way in my career in industry. Most users of computational chemistry want to know what small handful of methods can be applied broadly to large classes of problems. As experts, we are the group that is defining the next generation of standard methods so I find it very useful to know in what directions we are heading. Learning why we are using functionals can also let the developer of the "next big thing" know when their efforts to publicize and promote their methodology has fallen short and inspire them to better efforts in the future. Bill Laidig -----Original Message----- > From: owner-chemistry+laidig.wd==pg.com,ccl.net [mailto:owner-chemistry+laidig.wd==pg.com,ccl.net] On Behalf Of Robert Molt Jr r.molt.chemical.physics!=!gmail.com Sent: Sunday, June 01, 2014 3:07 PM To: Laidig, Bill Subject: CCL: DFT14poll Sent to CCL by: Robert Molt Jr [r.molt.chemical.physics]_[gmail.com] Sirs and Madames: A "popularity contest" is anathema to science. The world should not weight the opinion of Rodney Bartlett and Robert Molt equally in coupled cluster theory. Perhaps we should take a poll on what people think the first spherical harmonic is? Or take a poll on whether Planck's constant is too small? Evidence and and logic drive science. -Robert Molt On 06/01/2014 12:26 PM, Víctor Luaña Cabal victor,fluor.quimica.uniovi.es wrote: > Sent to CCL by: =?iso-8859-1?Q?V=EDctor_Lua=F1a?= Cabal > [victor-.-fluor.quimica.uniovi.es] > On Sun, Jun 01, 2014 at 06:01:52AM +0000, Rzepa, Henry S h.rzepa:imperial.ac.uk wrote: >> Can I suggest that in future this poll be extended to indicate WHY any person indicates they LIKE a functional? As we all know, the choice of functional so often depends on what the property of interest is. >> >> I suggest initially a relatively short controlled list of properties, >> which can then be extended by “crowd sourcing”. Properties I have >> in mind might be eg >> >> 1. Reaction barriers >> 2. Normal mode analysis >> 3. Chiroptical properties >> 4. Hydrogen bonds >> 5. Excitation energies >> 6. Main group elements >> 7. Transition metals >> 8. Relativistic elements >> 9. NMR shieldings, NMR couplings >> 10. etc >> >> That way, we could find out eg the most liked functional for eg >> looking at hydrogen bonds. That would be enormously helpful to >> anyone looking to study eg hydrogen bonds. > Dear Prof. Rzepa, > > I have a deep respect for your work, that I use to love, but in this > case I dislike strongly the idea of deciding the use of a functional > by popularity. There are plenty of examples in which the most popular > route was not the best, just the easiest. It took decades, in many > cases, to turn back wrong but popular decisions. Two candidates should > be advised to create a safe road: the easiest AND the the best > founded. Notice that the most popular is not in my list. Popularity > can be obtained by well studied techniques that have nothing to do > with any real measurement of quality. > > As for your list of properties it is very useful and I will keep it > carefully. > > Best regards, > Dr. Víctor Luaña > > -- > \|/ > |^.^| > +---!OO--\_/--OO!------------------------------+---------------------- > +- > ! Dr.Víctor Luaña ! > ! Departamento de Química Física y Analítica ! > ! Universidad de Oviedo, 33006-Oviedo, Spain ! > ! e-mail: victor*fluor.quimica.uniovi.es ! > ! phone: +34-985-103491 fax: +34-985-103125 ! > +----------------------------------------------+ > 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