<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">Hello,<div class=""><br class=""></div><div class="">Maybe the difference you are referring to is that between what theoretical chemist consider as "ab initio" and what physicists do.</div><div class=""><br class=""></div><div class="">This was a matter of controversy in the 1990’s, and to me, is more philosophical that physical.</div><div class=""><br class=""></div><div class="">For theoretical chemist, ab initio methods are methods based on the wavefunction, namely Hartee-Fock, and post-Hartree-Fock techniques (e.g., CAS-MCSCF, coupled cluster, CISD, Full-CI). In this sense, DFT is not ab initio as the main ingredient of DFT is the electron density, which is obtained from an approximate description of XC interelectronic interactions.</div><div class=""><br class=""></div><div class="">For physicists DFT is ab initio as the method is grounded on a theorem (HK one) and "starts from scratch".</div><div class=""><br class=""></div><div class="">Final note: for Walter Kohn, DFT is ab initio, not a semi-empirical methods (as many people coming from the community of theoretical chemists used to claim in the 1990’s), but its usage (LDA, GGA,…) is "something else » (if I remember well he said "it is just physics », [of interelectronic interactions]), as it relies on approximations in the XC functionals.</div><div class=""><br class=""></div><div class="">Today, this controversy has been shelved, and everybody, as far as I could see, use indiscernibly DFT or ab initio.</div><div class=""><br class=""></div><div class="">Best,</div><div class="">Pascal</div><div class=""><br class=""><div><br class=""><blockquote type="cite" class=""><div class="">Le 7 juil. 2022 à 13:59, Fecher, Gerhard <<a href="mailto:fecher@uni-mainz.de" class="">fecher@uni-mainz.de</a>> a écrit :</div><br class="Apple-interchange-newline"><div class=""><div class="">This is an unsuitable question, you ask what is the difference between<br class="">"from the beginning" and "density functional theory"<br class=""><br class="">probably one can speculate whether you might mean<br class=""> " What is the difference between "Hartre Fock", "Hohenberg Kohn", and "Kohn Sham" theoretical approaches to the elecstronic structure of atoms, molecules, or solids?"<br class="">In that case, a good textbook or the original works might help you the latter rather better than second hand multiple genealogy references ==> do your study ab initio !<br class=""><br class="">Ciao<br class="">Gerhard<br class=""><br class="">DEEP THOUGHT in D. Adams; Hitchhikers Guide to the Galaxy:<br class="">"I think the problem, to be quite honest with you,<br class="">is that you have never actually known what the question is."<br class=""><br class="">====================================<br class="">Dr. Gerhard H. Fecher<br class="">Institut of Physics<br class="">Johannes Gutenberg - University<br class="">55099 Mainz<br class="">________________________________________<br class="">Von: Wien [<a href="mailto:wien-bounces@zeus.theochem.tuwien.ac.at" class="">wien-bounces@zeus.theochem.tuwien.ac.at</a>] im Auftrag von ben amara imen [<a href="mailto:imen.benamara5@gmail.com" class="">imen.benamara5@gmail.com</a>]<br class="">Gesendet: Mittwoch, 6. Juli 2022 15:18<br class="">An: <a href="mailto:wien@theochem.tuwien.ac.at" class="">wien@theochem.tuwien.ac.at</a>; <a href="mailto:wien@zeus.theochem.tuwien.ac.at" class="">wien@zeus.theochem.tuwien.ac.at</a><br class="">Betreff: [Wien] Ab inition and DFT<br class=""><br class="">Dears users<br class=""><br class="">Can someone please explain the difference between ab initio calculation and DFT.<br class=""><br class="">As I know , ab initio calculation is based on wave function without any empirical parameters . DFT is based on density of charge but it uses the empirical parameters (within Exchange-correlation potentiel PBE , GGA..).<br class=""><br class="">Is it correct ?.<br class=""><br class="">If it is correct , why some papers consider DFT as ab initio calculation.<br class=""><br class="">Thanks<br class=""><br class=""><br class="">Best regards<br class="">_______________________________________________<br class="">Wien mailing list<br class=""><a href="mailto:Wien@zeus.theochem.tuwien.ac.at" class="">Wien@zeus.theochem.tuwien.ac.at</a><br class="">http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien<br class="">SEARCH the MAILING-LIST at: http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html<br class=""></div></div></blockquote></div><br class=""><div class="">
<div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div class=""><font face="Brush Script MT" size="4" class="">Pascal Boulet</font></div><div class=""><span style="font-size: 21px; font-family: "Lucida Handwriting";" class="">—</span></div><div class=""><em class="" style="color: rgb(34, 187, 234); font-family: verdana; font-size: 11px; line-height: 22px;">Professor in computational materials chemistry - DEPARTMENT OF CHEMISTRY</em></div><div class=""><div class="" style="font-family: Tahoma, Verdana, Arial, Helvetica, sans-serif; font-size: 15px; line-height: 22px;"><span class="" style="font-size: 11px; font-family: verdana;">University of Aix-Marseille </span><span class="" style="font-size: 11px; font-family: verdana;">- Avenue Escadrille Normandie Niemen - F-13013 Marseille - FRANCE</span></div><div class="" style="font-family: Tahoma, Verdana, Arial, Helvetica, sans-serif; font-size: 15px; line-height: 22px;"><span class="" style="font-size: 11px; font-family: verdana;">Tél: +33(0)4 13 55 18 10 - Fax : +33(0)4 13 55 18 50</span></div><div class=""><font face="Verdana" class=""><span style="font-style: normal; font-size: 11px;" class=""><font class=""><span class="" style="line-height: 22px;">Email : </span></font><font color="#22bbea" class=""><span style="line-height: 20px;" class=""><a href="mailto:pascal.boulet@univ-amu.fr" class="">pascal.boulet@univ-amu.fr</a></span></font></span></font></div><div class=""><font color="#22bbea" face="verdana" class=""><br class=""></font></div></div></div><br class="Apple-interchange-newline"><br class="Apple-interchange-newline">
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