tag:blogger.com,1999:blog-13869903.post6191218131493033995..comments2024-03-29T02:45:10.096-05:00Comments on nanoscale views: What is density functional theory? part 1.Douglas Natelsonhttp://www.blogger.com/profile/13340091255404229559noreply@blogger.comBlogger2125tag:blogger.com,1999:blog-13869903.post-35298549474254049272016-02-03T07:39:31.775-06:002016-02-03T07:39:31.775-06:00Anon, the basic reasoning is: You can prove rigor...Anon, the basic reasoning is: You can prove rigorously that the density as a fn of position alone tells you everything about the ground state (! very surprising, on its face !), and there is a procedure involving non-interacting electrons that can get you arbitrarily close to the true density a fn of position. In principle, if you knew how to write down the exchange-correlation piece of the functional and do the math in a computationally efficient way, you could get exact answers. That was Russ McKenzie's point in the post that I linked in my first writing about this.<br /><br />I'm not arguing that DFT is flawless, but you are giving it very short shrift by implying that it's some epicycle-like farce or that it's widespread utility is a scandal. It's also not the only game in town, and it does actually make quantitative, testable predictions. (which I will discuss further shortly) Douglas Natelsonhttps://www.blogger.com/profile/13340091255404229559noreply@blogger.comtag:blogger.com,1999:blog-13869903.post-52202802052044294142016-02-03T03:05:45.743-06:002016-02-03T03:05:45.743-06:00I admit I don't know anything about this but i...I admit I don't know anything about this but it seems the basic reasoning is as follows:<br /><br />Reduce the many-electron *interacting* problem to a non-interacting 1-electron system.<br /><br />I assume this is an abuse of mathematics because by definition correlation is everything that cannot by covered at the 1-electron level.<br /><br />Anyways, at the practical level, "success" of DFT is made possible by incorporating empirical methods and benchmarking against wave function based calculations. So why is it so fantastic if it is not reliable for even the simplest systems and the alphabet zoo of functionals makes it so-called simplicity a farce?<br /><br />Its as if condensed matter has its own scandal going similar to string theory. DFT, only game in town...the record citations prove it.Anonymousnoreply@blogger.com