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This article was the subject of a Wiki Education Foundation-supported course assignment, between 10 March 2020 and 30 April 2020. Further details are available on the course page. Student editor(s): Natefoulk4. Peer reviewers: Nduc5420.
Above undated message substituted from Template:Dashboard.wikiedu.org assignment by PrimeBOT ( talk) 19:19, 16 January 2022 (UTC)
The page is inconsistent in whether "density-functional" is hyphenated or not. Perhaps most egregiously, the article title is not hyphenated but the bold term right below it that starts the article is hyphenated. I'm partial to hyphenating it, but I'd prefer to leave it to others more familiar with the field and how the term is generally used to make the decision. 172.92.14.139 ( talk) 16:51, 26 October 2022 (UTC)
In my opinion, the explanation given for a functional in the second sentence is not complete, because by function of a function it is meant f(g(x)), while a functional can be whatever application defined on a space of functions. This definition includes functions of functions but also other kinds of application (a common one is the integral over an interval [a,b] of the function). Francesco.randi ( talk) 15:36, 23 March 2012 (UTC)
Mott insulators are quite an important example of DFT not working as it could in strongly correlated electron systems. Do you think it's worth mentioning specifically. I don't know if it is comparable to the examples given in other fields. Grj23 ( talk) 21:01, 1 April 2009 (UTC)
When discussing DFT and dispersion forces I would be more careful in saying that"Despite the improvements in DFT, there are still difficulties in using density functional theory to properly describe intermolecular interactions, especially van der Waals forces (dispersion)". In literature there are some examples of how to address this issue. In particular, it has been shown that the BHandH functional is able of reproducing with great accuracy correlated ab initio performances, see for instance "Hybrid density functional theory for pi-stacking interactions: application to benzenes, pyridines, and DNA bases", Robertazzi et al., Journal of Computional Chemistry, 2006 Mar;27(4):491-504.
I would explain the different opinions about DFT vs ab initio. While DFT is able to treat bigger, more complex systems, many scientists view it just as a good semiempyrical technique, not to be used if a "proper" ab initio calculation is possible.
True, also should be mentioned are techniques that are less accurate than DFT but can be used for bigger systems still.
DFT is not in itself semi-empirical (Hohenberg-Kohn is in itself just a reformulation of the Schrodinger equation.) LDA and LSDA are ab initio. Many popular functionals are however semi-empirical.
But the debate on true ab initio vs. hybrid DFT may be a bit too specific for a general article such as this though. Although DFT looks somewhat empirical in comparison to wave-based methods, by comparison to the very empirical methods such as MM, DFT looks very 'ab initio' indeed.
I made some changes to the introduction of the article. I felt some statements were incorrect, or at least very vague. For example, the sentence beginning with "Within the framework of DFT, the ..." actually describes Kohn-Sham theory. DFT, of course, can be done without Kohn-Sham (see the original Hohenberg-Kohn paper).
The same sentence says that DFT reduces the many body problem to a "solvable problem of a single electron moving in an averaged effective force field." Being picky and precise, I don't think this is true. DFT does not reduce the N-body problem to a single electron problem, Kohn-Sham reduces it to an effective non-interacting electron problem. Moreover, this is not always solvable: if you have electrons you still cannot solve the equivalent non-interacting problem. Where, by solve, I mean to numerically solve the problem.
I will probably make more modifications, further down the article, as time goes on. I know that some of the material in the introduction is now repeated later, but that shouldn't be a big deal. Please comment. WikipAcct 07:58, 2 Jan 2005 (UTC)
Also, I think the article needs to emphasize that KS-DFT is a groundstate theory. And it should mention the time-dependent generalization. I will add these to the to-do list.
The statement: DFT is an exact theory only for the free electron gas, while for the treatment of extended atomic systems various approximations have to be made, is slightly misleading.
The paradigm of DFT development, starting with Thomas-Fermi and Kohn-Sham has been to work as a series of corrections to the free electron gas model. All functionals I know of use that approach, and can thus be said to be 'exact for the free electron gas'. But this does not mean DFT by necessity is like that. DFT can in principle be exact for any potential fullfilling the criterium of the Hohenberg-Kohn proof.
Some of the statements seemed to be still odd, and so i cleaned up some sections, and expanded some. I think it still needs a discussion of time-dependent DFT, as well as some more applications, and maybe some of the work on including dispersion into functionals. Salsb 18:30, 26 July 2005 (UTC)
If I may add something: The Spartan package distributed by Wavefunction, Inc. also supports DFT computations. The version we are running in our laboratory is properly cited as: Spartan'04 for Macintosh; Wavefunction, Inc.; Irvine, CA. Iamthealchemist 22:03, 6 December 2005 (UTC)
I think there needs to be more on the various exchange and correlation functions that are widely used, particularly in programs such as Gaussian. There is a mention of B3LYP without stating that it is a hybrid method and this needs defining as noted on the TODO list above. There is no mention of non-hybrid methods such as BLYP. Elsewhere there is an empty link to B3LYP, so perhaps we need a set of sections on different widely used methods, so they can be used as links for B3LYP and so on. I am rather busy at present with other pages and I am not a real expert on DFT. Anyone else want to do it? Bduke 01:02, 19 December 2005 (UTC)
Which part of Kohn-Sham equations is the "Kohn-Sham functional"? -- HappyCamper 14:14, 4 October 2006 (UTC)
I think it might be helpful to separate the list of software that supports DFT into programs available for free (including GPL'd software and proprietary software released gratis) and programs for which a paid site license is required. Does this make sense? -- WilliamJenkins09 ( talk) 14:02, 4 January 2008 (UTC)
Seems like the section, Description of the theory, is out of place. It could be to merged with the lead (which needs beefing up anyway), placed above the Hohenberg-Kohn theorems section, or a bit of both. Part of the last paragraph in that section could be expanded in to a general overview of the issues that are still being worked out with DFT and placed in a section of its own lower down the article. Also the Thomas-Fermi model section could be expanded in to an article of its own having only a brief comment in this article. Any of these suggestions sound reasonable? THEN WHO WAS PHONE? ( talk) 19:28, 2 November 2008 (UTC)
I'm in the process of deleting some text with mathematical details about how to calculate electron chemical potential within DFT. It is this section here. It is too specialized to keep within the general chemical potential article. If someone knows a good home for it, either this article or somewhere else, please feel free to put it there. Thanks! -- Steve ( talk) 14:13, 27 April 2012 (UTC)
When the article is describing LDA, it says "the functional depends only on the density at the coordinate where the functional is evaluated". However, the functional isn't evaluated at a particular coordinate in space, r. The functional is an integral over all points in space. The "coordinate" of the functional is the density function, not a location, r. Mpalenik ( talk) 02:11, 14 March 2013 (UTC)
This article is structurally weird, tacking on the whole classical DFT topic after what feels like the end of a complete article on quantum QFT. Plus, wading through all this quantum stuff is frustrating when searching for information on classical DFT. German wikipedia has two separate articles and I found it more readable. However, an ambitious undertaking and I'm personally struggling to understand either. CyreJ ( talk) 10:41, 13 January 2022 (UTC)
The dimensions in the equation do not add up.
Also, a clarification, that is not the chemical potential in the sense of being the intensive variable to particle number, but that , where is the external potential, would in my opinion be an improvement. FNGdM ( talk) 17:05, 31 August 2023 (UTC)
This
level-5 vital article is rated C-class on Wikipedia's
content assessment scale. It is of interest to the following WikiProjects: | |||||||||||||||||||||
|
To-do list for Density functional theory:
|
This article was the subject of a Wiki Education Foundation-supported course assignment, between 10 March 2020 and 30 April 2020. Further details are available on the course page. Student editor(s): Natefoulk4. Peer reviewers: Nduc5420.
Above undated message substituted from Template:Dashboard.wikiedu.org assignment by PrimeBOT ( talk) 19:19, 16 January 2022 (UTC)
The page is inconsistent in whether "density-functional" is hyphenated or not. Perhaps most egregiously, the article title is not hyphenated but the bold term right below it that starts the article is hyphenated. I'm partial to hyphenating it, but I'd prefer to leave it to others more familiar with the field and how the term is generally used to make the decision. 172.92.14.139 ( talk) 16:51, 26 October 2022 (UTC)
In my opinion, the explanation given for a functional in the second sentence is not complete, because by function of a function it is meant f(g(x)), while a functional can be whatever application defined on a space of functions. This definition includes functions of functions but also other kinds of application (a common one is the integral over an interval [a,b] of the function). Francesco.randi ( talk) 15:36, 23 March 2012 (UTC)
Mott insulators are quite an important example of DFT not working as it could in strongly correlated electron systems. Do you think it's worth mentioning specifically. I don't know if it is comparable to the examples given in other fields. Grj23 ( talk) 21:01, 1 April 2009 (UTC)
When discussing DFT and dispersion forces I would be more careful in saying that"Despite the improvements in DFT, there are still difficulties in using density functional theory to properly describe intermolecular interactions, especially van der Waals forces (dispersion)". In literature there are some examples of how to address this issue. In particular, it has been shown that the BHandH functional is able of reproducing with great accuracy correlated ab initio performances, see for instance "Hybrid density functional theory for pi-stacking interactions: application to benzenes, pyridines, and DNA bases", Robertazzi et al., Journal of Computional Chemistry, 2006 Mar;27(4):491-504.
I would explain the different opinions about DFT vs ab initio. While DFT is able to treat bigger, more complex systems, many scientists view it just as a good semiempyrical technique, not to be used if a "proper" ab initio calculation is possible.
True, also should be mentioned are techniques that are less accurate than DFT but can be used for bigger systems still.
DFT is not in itself semi-empirical (Hohenberg-Kohn is in itself just a reformulation of the Schrodinger equation.) LDA and LSDA are ab initio. Many popular functionals are however semi-empirical.
But the debate on true ab initio vs. hybrid DFT may be a bit too specific for a general article such as this though. Although DFT looks somewhat empirical in comparison to wave-based methods, by comparison to the very empirical methods such as MM, DFT looks very 'ab initio' indeed.
I made some changes to the introduction of the article. I felt some statements were incorrect, or at least very vague. For example, the sentence beginning with "Within the framework of DFT, the ..." actually describes Kohn-Sham theory. DFT, of course, can be done without Kohn-Sham (see the original Hohenberg-Kohn paper).
The same sentence says that DFT reduces the many body problem to a "solvable problem of a single electron moving in an averaged effective force field." Being picky and precise, I don't think this is true. DFT does not reduce the N-body problem to a single electron problem, Kohn-Sham reduces it to an effective non-interacting electron problem. Moreover, this is not always solvable: if you have electrons you still cannot solve the equivalent non-interacting problem. Where, by solve, I mean to numerically solve the problem.
I will probably make more modifications, further down the article, as time goes on. I know that some of the material in the introduction is now repeated later, but that shouldn't be a big deal. Please comment. WikipAcct 07:58, 2 Jan 2005 (UTC)
Also, I think the article needs to emphasize that KS-DFT is a groundstate theory. And it should mention the time-dependent generalization. I will add these to the to-do list.
The statement: DFT is an exact theory only for the free electron gas, while for the treatment of extended atomic systems various approximations have to be made, is slightly misleading.
The paradigm of DFT development, starting with Thomas-Fermi and Kohn-Sham has been to work as a series of corrections to the free electron gas model. All functionals I know of use that approach, and can thus be said to be 'exact for the free electron gas'. But this does not mean DFT by necessity is like that. DFT can in principle be exact for any potential fullfilling the criterium of the Hohenberg-Kohn proof.
Some of the statements seemed to be still odd, and so i cleaned up some sections, and expanded some. I think it still needs a discussion of time-dependent DFT, as well as some more applications, and maybe some of the work on including dispersion into functionals. Salsb 18:30, 26 July 2005 (UTC)
If I may add something: The Spartan package distributed by Wavefunction, Inc. also supports DFT computations. The version we are running in our laboratory is properly cited as: Spartan'04 for Macintosh; Wavefunction, Inc.; Irvine, CA. Iamthealchemist 22:03, 6 December 2005 (UTC)
I think there needs to be more on the various exchange and correlation functions that are widely used, particularly in programs such as Gaussian. There is a mention of B3LYP without stating that it is a hybrid method and this needs defining as noted on the TODO list above. There is no mention of non-hybrid methods such as BLYP. Elsewhere there is an empty link to B3LYP, so perhaps we need a set of sections on different widely used methods, so they can be used as links for B3LYP and so on. I am rather busy at present with other pages and I am not a real expert on DFT. Anyone else want to do it? Bduke 01:02, 19 December 2005 (UTC)
Which part of Kohn-Sham equations is the "Kohn-Sham functional"? -- HappyCamper 14:14, 4 October 2006 (UTC)
I think it might be helpful to separate the list of software that supports DFT into programs available for free (including GPL'd software and proprietary software released gratis) and programs for which a paid site license is required. Does this make sense? -- WilliamJenkins09 ( talk) 14:02, 4 January 2008 (UTC)
Seems like the section, Description of the theory, is out of place. It could be to merged with the lead (which needs beefing up anyway), placed above the Hohenberg-Kohn theorems section, or a bit of both. Part of the last paragraph in that section could be expanded in to a general overview of the issues that are still being worked out with DFT and placed in a section of its own lower down the article. Also the Thomas-Fermi model section could be expanded in to an article of its own having only a brief comment in this article. Any of these suggestions sound reasonable? THEN WHO WAS PHONE? ( talk) 19:28, 2 November 2008 (UTC)
I'm in the process of deleting some text with mathematical details about how to calculate electron chemical potential within DFT. It is this section here. It is too specialized to keep within the general chemical potential article. If someone knows a good home for it, either this article or somewhere else, please feel free to put it there. Thanks! -- Steve ( talk) 14:13, 27 April 2012 (UTC)
When the article is describing LDA, it says "the functional depends only on the density at the coordinate where the functional is evaluated". However, the functional isn't evaluated at a particular coordinate in space, r. The functional is an integral over all points in space. The "coordinate" of the functional is the density function, not a location, r. Mpalenik ( talk) 02:11, 14 March 2013 (UTC)
This article is structurally weird, tacking on the whole classical DFT topic after what feels like the end of a complete article on quantum QFT. Plus, wading through all this quantum stuff is frustrating when searching for information on classical DFT. German wikipedia has two separate articles and I found it more readable. However, an ambitious undertaking and I'm personally struggling to understand either. CyreJ ( talk) 10:41, 13 January 2022 (UTC)
The dimensions in the equation do not add up.
Also, a clarification, that is not the chemical potential in the sense of being the intensive variable to particle number, but that , where is the external potential, would in my opinion be an improvement. FNGdM ( talk) 17:05, 31 August 2023 (UTC)