From owner-chemistry@ccl.net Sun Apr 19 08:22:01 2015 From: "=?iso-8859-1?Q?V=EDctor_Lua=F1a?= Cabal victor(_)fluor.quimica.uniovi.es" To: CCL Subject: CCL:G: Optimization in Z-matrix vs Cartesian coordinates Message-Id: <-51270-150419081341-6376-epf3gUDiYvdbo6jxNKi2Zw/a\server.ccl.net> X-Original-From: =?iso-8859-1?Q?V=EDctor_Lua=F1a?= Cabal Content-disposition: inline Content-transfer-encoding: 8BIT Content-type: text/plain; charset=iso-8859-1 Date: Sun, 19 Apr 2015 14:06:31 +0200 MIME-version: 1.0 Sent to CCL by: =?iso-8859-1?Q?V=EDctor_Lua=F1a?= Cabal [victor##fluor.quimica.uniovi.es] On Sat, Apr 18, 2015 at 09:45:42PM +0400, Grigoriy Zhurko reg_zhurko/achemcraftprog.com wrote: > > Sent to CCL by: Grigoriy Zhurko [reg_zhurko__chemcraftprog.com] > I initially supposed that a geometry optimization, if it is performed > in properly composed Z-matrix, takes less optimization steps than if it > runs in Cartesian coordinates. Is that wrong? A properly constructed > Z-matrix, as far as I suppose, must use dummy atoms for each aromatic > cycle in the molecule (the dummy atom is placed in the center of > a cycle). > I don't mean here the symmetry constraints. I want to compare the > speed of geometry optimization of a non-symmetrical molecule (C1) > in Z-matrix and Cartesian coordinates. > I have this question because I have implemented automatic generation > of Z-matrix in my program Chemcraft, and I wonder whether this feature > can be useful. I appreciate any suggestions, in which cases such feature > can be used. Grigoriy, 1) Last time I taught quantum chemistry I prepared for my students some slides showing the importance of exploring several ways for optimizing the geometry of a molecule. 2) The examples are too simple to show here, but the lesson to consider is that every major quantum code (gamess, gaussian, UK-gamess, nwchem, columbus, dalton, adf, quantum-expresso, wien2k, orca, molcas, jaguar, ...) has tricks regarding how to drive optimizations 3) The task is far from trivial and, unfortunately, many of the tricks are hidden in shells of code hard to follow. Some have never been documented properly. 4) Some traditional repositories of code have disappeared, like the Indiana quantum chemistry exchange. Old programmers are retiring or worse. That's life ... 5) I had to do some days ago an estimation of the effort invested in programming a major quantum chemistry code: gaussian is now 50 years old. If we assume some 8 groups of developpers, 2 main programmers for group, 300 days working per year, 8 hour per day that eould be 1920000 hours ~ 220 years 6) It's clear the huge invest in developping a major code. 7) Proper citation of the codes used for any study is not only correct and ethic. It's an obligation for any group interested in the advancement of computational science. 8) In the software part of our web any may find source codes to explore and, eventually, use: Best regards, Dr. Víctor Luaña -- . . DEEP THOUGHT in D. Adams; Hitchhikers Guide to the Galaxy: / `' \ "I think the problem, to be quite honest with you, /(o)(o)\ is that you have never actually known what the question is." /`. \/ .'\ / '`'` \ "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, in silico chemist & prof. ! 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)