From owner-chemistry@ccl.net Thu Jul 26 07:18:00 2018 From: "Herbert Fruchtl herbert.fruchtl : st-andrews.ac.uk" To: CCL Subject: CCL:G: Mixed Gaussian and plane-wave DFT Message-Id: <-53417-180726071352-28490-n8/Nkx2NybmKubXNkwYYmw[]server.ccl.net> X-Original-From: Herbert Fruchtl Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=windows-1252; format=flowed Date: Thu, 26 Jul 2018 12:13:37 +0100 MIME-Version: 1.0 Sent to CCL by: Herbert Fruchtl [herbert.fruchtl/./st-andrews.ac.uk] There are different "mixed basis" approaches for periodic systems. In the case of CP2K, you essentially use atom centred basis sets. The plane waves only come in as an expansion basis to make the calculation of integrals more efficient, but all orbitals are expressed in Gaussians following the LCAO approach. This means you have to put some thought into choosing the right basis set (not just a cut-off as in pure plane-wave codes). You also have BSSE, which is an error introduced by the fact that the basis set is geometry dependent. This differs from muffin-tin based approaches (such as FLAPW), where you have atom centred basis functions to describe the atoms (or rather the area close to the nuclei, since there is no such thing as an atom...) and plane waves for the space in between. Hope this helps, Herbert On 26/07/18 04:42, Andrew Scott Rosen rosen:+:u.northwestern.edu wrote: > > Sent to CCL by: "Andrew Scott Rosen" [rosen]*[u.northwestern.edu] > Dear compchem listserv, > > Does anyone here have familiarity with the mixed Gaussian and plane-wave > (i.e. GPW) approach used in CP2K for periodic DFT? If so, what are the > limitations of the GPW method in CP2K compared to periodic DFT codes that > just use plane-waves, such as VASP? Are there any? > > Andrew> > -- Herbert Fruchtl Senior Scientific Computing Officer School of Chemistry, School of Mathematics and Statistics University of St Andrews -- The University of St Andrews is a charity registered in Scotland: No SC013532