Re: [Wien] Relaxation of already known structure
Dear All, Thank you for your replied all. It helps me a lot. I usually only calculate magnetic properties, and it seems like that the relaxation does not affect the magnetic properties much (at least the material I calculate now). I am wondering if the other properties are affected a lot more. Because two of my coworkers in another university told me that the relaxation must be performed for all calculations. I am still not sure how to convince myself. If the magnetic properties for relaxed structure is a little bit different from the magnetic properties for experimental (not relaxed) structure, what results should I believe? Should I just believe the results that are close to experimental magnetic properties? Then why the expert Dr. Novak did not do the relaxation? Is it because the relaxation for the known structures is really not needed? All my best, Jihoon Park On Mon, Jul 21, 2014 at 2:59 PM, Víctor Luaña < vic...@fluor.quimica.uniovi.es> wrote: > On Mon, Jul 21, 2014 at 02:16:27PM -0500, Jihoon Park wrote: > > I am wondering if we must do the relaxation for all calculations. > > I have found some first principles studies with experimental lattice > > constants, including Dr. Novak's work "PRB 71, 1844422 (2005)." > > Therefore, I need to know if the first principles calculations with > > experimental lattice constants are reliable or in what case, it is good > > enough or somethings. > > Could anybody please give me some guidance? > > It depends very much on your intention. Optimizing an structure can be > taken as a test of how appropriate is your calculation method for the > system you are trying to analyze. The experimental value is the thing > you are trying to reproduce, but not all experiments are done under > the same precision, nor all experiments provide a well defined result. > > Remember that science is understanding, not only producing tables > of numbers. Very simple models have been fundamental in science. > For instance we owe our periodic table of the elements basically to > ideas and concepts generated before quantum mechanics. > > It is not wrong, of course, the use a simple well defined recipe on a > large collection of compounds trying to get some systematic rule. > > So, try to learn from the literature in your field and try to follow > an unexploited road from the best starting point. Not a simple way but > remember: It is easy to imagine a simple solution for a complex problem > ... the pity is that most are wrong! > > Best regards, > Dr. Víctor Luaña > > -- >\|/a "After years of working on a problem the genius shout: > |^.^| what an idiot I am ... the solution is trivial!' > +-!OO--\_/--OO!--+--- > !Dr.Víctor Luaña ! > ! Departamento de Química Física y Analítica ! > ! Universidad de Oviedo, 33006-Oviedo, Spain ! > ! e-mail: vic...@fluor.quimica.uniovi.es ! > ! phone: +34-985-103491 fax: +34-985-103125 ! > +--+ > GroupPage : http://azufre.quimica.uniovi.es/ (being reworked) > ___ > Wien mailing list > Wien@zeus.theochem.tuwien.ac.at > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien > SEARCH the MAILING-LIST at: > http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html > ___ Wien mailing list Wien@zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien SEARCH the MAILING-LIST at: http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html
Re: [Wien] Relaxation of already known structure
On Mon, Jul 21, 2014 at 02:16:27PM -0500, Jihoon Park wrote: > I am wondering if we must do the relaxation for all calculations. > I have found some first principles studies with experimental lattice > constants, including Dr. Novak's work "PRB 71, 1844422 (2005)." > Therefore, I need to know if the first principles calculations with > experimental lattice constants are reliable or in what case, it is good > enough or somethings. > Could anybody please give me some guidance? It depends very much on your intention. Optimizing an structure can be taken as a test of how appropriate is your calculation method for the system you are trying to analyze. The experimental value is the thing you are trying to reproduce, but not all experiments are done under the same precision, nor all experiments provide a well defined result. Remember that science is understanding, not only producing tables of numbers. Very simple models have been fundamental in science. For instance we owe our periodic table of the elements basically to ideas and concepts generated before quantum mechanics. It is not wrong, of course, the use a simple well defined recipe on a large collection of compounds trying to get some systematic rule. So, try to learn from the literature in your field and try to follow an unexploited road from the best starting point. Not a simple way but remember: It is easy to imagine a simple solution for a complex problem ... the pity is that most are wrong! Best regards, Dr. Víctor Luaña -- \|/a "After years of working on a problem the genius shout: |^.^| what an idiot I am ... the solution is trivial!' +-!OO--\_/--OO!--+--- !Dr.Víctor Luaña ! ! Departamento de Química Física y Analítica ! ! Universidad de Oviedo, 33006-Oviedo, Spain ! ! e-mail: vic...@fluor.quimica.uniovi.es ! ! phone: +34-985-103491 fax: +34-985-103125 ! +--+ GroupPage : http://azufre.quimica.uniovi.es/ (being reworked) ___ Wien mailing list Wien@zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien SEARCH the MAILING-LIST at: http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html
Re: [Wien] Relaxation of already known structure
For totally symmetric structures forces are zero, for example NaCl, Li2O, so the forces criterion does not apply! De: wien-boun...@zeus.theochem.tuwien.ac.at en nombre de Parker, David S. Enviado: lunes, 21 de julio de 2014 02:42 p.m. Para: A Mailing list for WIEN2k users Asunto: Re: [Wien] Relaxation of already known structure Jihoon, it depends on the sensitivity of the calculations. I generally always use the experimental lattice constants, and then relax the internal coordinates if forces are significant - greater than 5 or so mRyd/bohr (the units WIEN uses). But this takes a lot longer than a simple scf run and often has little, if any effect on the results. For a first pass at a calculation, unless the forces are huge, I don't do a relaxation. If the result is interesting enough that a publication may result, then I do a relaxation. Best, David Parker From: Jihoon Park mailto:maximumenergyprod...@gmail.com>> Reply-To: A users mailto:wien@zeus.theochem.tuwien.ac.at>> Date: Monday, July 21, 2014 3:16 PM To: A users mailto:wien@zeus.theochem.tuwien.ac.at>> Subject: [Wien] Relaxation of already known structure Dear Users, I am wondering if we must do the relaxation for all calculations. I have found some first principles studies with experimental lattice constants, including Dr. Novak's work "PRB 71, 1844422 (2005)." Therefore, I need to know if the first principles calculations with experimental lattice constants are reliable or in what case, it is good enough or somethings. Could anybody please give me some guidance? All my best Jihoon Park ___ Wien mailing list Wien@zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien SEARCH the MAILING-LIST at: http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html ___ Wien mailing list Wien@zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien SEARCH the MAILING-LIST at: http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html
Re: [Wien] Relaxation of already known structure
Jihoon, it depends on the sensitivity of the calculations. I generally always use the experimental lattice constants, and then relax the internal coordinates if forces are significant - greater than 5 or so mRyd/bohr (the units WIEN uses). But this takes a lot longer than a simple scf run and often has little, if any effect on the results. For a first pass at a calculation, unless the forces are huge, I don't do a relaxation. If the result is interesting enough that a publication may result, then I do a relaxation. Best, David Parker From: Jihoon Park mailto:maximumenergyprod...@gmail.com>> Reply-To: A users mailto:wien@zeus.theochem.tuwien.ac.at>> Date: Monday, July 21, 2014 3:16 PM To: A users mailto:wien@zeus.theochem.tuwien.ac.at>> Subject: [Wien] Relaxation of already known structure Dear Users, I am wondering if we must do the relaxation for all calculations. I have found some first principles studies with experimental lattice constants, including Dr. Novak's work "PRB 71, 1844422 (2005)." Therefore, I need to know if the first principles calculations with experimental lattice constants are reliable or in what case, it is good enough or somethings. Could anybody please give me some guidance? All my best Jihoon Park ___ Wien mailing list Wien@zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien SEARCH the MAILING-LIST at: http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html
Re: [Wien] Relaxation of already known structure
Experimental results are "the real thing", but usually the optimized parameters are close to these values, so you can use the experimental results. I did an optimization of Li2O2 to discern between 2 possible structures: Féher et al (1953) Chem. Ber. 86, 1429 Föppl (1957) Z. Anorg. Allg. Chem 291, 12 and with optimizations we were able to discard Féher's structure. De: wien-boun...@zeus.theochem.tuwien.ac.at en nombre de Jihoon Park Enviado: lunes, 21 de julio de 2014 02:16 p.m. Para: A Mailing list for WIEN2k users Asunto: [Wien] Relaxation of already known structure Dear Users, I am wondering if we must do the relaxation for all calculations. I have found some first principles studies with experimental lattice constants, including Dr. Novak's work "PRB 71, 1844422 (2005)." Therefore, I need to know if the first principles calculations with experimental lattice constants are reliable or in what case, it is good enough or somethings. Could anybody please give me some guidance? All my best Jihoon Park ___ Wien mailing list Wien@zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien SEARCH the MAILING-LIST at: http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html
[Wien] Relaxation of already known structure
Dear Users, I am wondering if we must do the relaxation for all calculations. I have found some first principles studies with experimental lattice constants, including Dr. Novak's work "PRB 71, 1844422 (2005)." Therefore, I need to know if the first principles calculations with experimental lattice constants are reliable or in what case, it is good enough or somethings. Could anybody please give me some guidance? All my best Jihoon Park ___ Wien mailing list Wien@zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien SEARCH the MAILING-LIST at: http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html
