From owner-nwchem-users@emsl.pnl.gov Sat Nov 24 16:35:45 2007 Received: from odyssey.emsl.pnl.gov (localhost [127.0.0.1]) by odyssey.emsl.pnl.gov (8.14.1/8.14.1) with ESMTP id lAP0ZiPa003887 for ; Sat, 24 Nov 2007 16:35:45 -0800 (PST) Received: (from majordom@localhost) by odyssey.emsl.pnl.gov (8.14.1/8.14.1/Submit) id lAP0ZiCS003886 for nwchem-users-outgoing-0915; Sat, 24 Nov 2007 16:35:44 -0800 (PST) X-Authentication-Warning: odyssey.emsl.pnl.gov: majordom set sender to owner-nwchem-users@emsl.pnl.gov using -f X-IronPort-AV: E=Sophos;i="4.21,462,1188802800"; d="scan'208";a="57521362" X-MimeOLE: Produced By Microsoft Exchange V6.5 Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Subject: RE: [NWCHEM] questions about PSPW Date: Sat, 24 Nov 2007 16:35:41 -0800 Message-ID: In-Reply-To: <809a4c910711210807j145322f3m44970c82cefa505b@mail.gmail.com> X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [NWCHEM] questions about PSPW thread-index: AcgsWUBm/5Mp5p9dR0CF1ZXeebiqmACn/IEg References: <809a4c910711210807j145322f3m44970c82cefa505b@mail.gmail.com> From: "Bylaska, Eric J" To: "Chona S. Guiang" , Cc: "Nichols, Patrick J" X-OriginalArrivalTime: 25 Nov 2007 00:35:42.0492 (UTC) FILETIME=[1C3455C0:01C82EFB] Sender: owner-nwchem-users@emsl.pnl.gov Precedence: bulk Chona, 1. In nwchem 5.0 the cutoff energy input is a little convoluted. It's probably best to enter both the energy_cutoff and the wavefunction_cutoff, such that the wavefunction cutoff is 1/2 the energy cutoff, e.g.: nwpw energy_cutoff 100.0 wavefunction_cutoff 50.0=20 end The code will automatically pick the ngrid. However, it is sometimes better to also enter ngrid, since sometimes the automatic grid generation enters weird grids. =20 2. In general the coordinate doesn't matter if the cutoff energies are high enough and the system is an insulator. =20 3. Using automatic gridding should give you good estimates for ngrid if you descide to use this option. One thing however, is that if you use the default parallel mapping then the second and third ngrid dimension will have to have the same value. If you want to have more freedom in the choice of cell then use mapping 2, i.e. nwpw mapping 2 end Finally, you may want to contact Patrick Nichols (patrick.nichols@pnl.gov) or use the opium pseudopotential package (opium.sourceforge.net) for a better Ti pseudopotential. The default Ti pseudopotential in 5.0 doesn't work very well with gradient corrected pseudopotentials.=20 With the upcoming release, nwchem 5.1, the definition of the cutoff energy has been simplified.=20 Hope that helps Eric Bylaska -----Original Message----- From: owner-nwchem-developers@emsl.pnl.gov [mailto:owner-nwchem-developers@emsl.pnl.gov] On Behalf Of Chona S. Guiang Sent: Wednesday, November 21, 2007 8:07 AM To: nwchem-users@emsl.pnl.gov Subject: [NWCHEM] questions about PSPW Hi, I would like to do some plane-wave DFT calculations on a TiO2 (110) slab consisting of 2x1 super cells with 4 Ti layers. I'm very new to this type of calculation so I took the pspw_SiC unit cell optimization as a template. I still have a few questions after reading the PSPW section of the user guide: 1. if I want to use plane waves with energy hbar^2 k^2/2m < E, do I use the "energy_cutoff E" option? 2. should I pay attention to the origin of the coordinate system used to specify the input geometry? 3. I'm not sure what values to set for NGRID in the SIMULATION CELL sub block. If I choose different values for NGRID will I get significant differences in the corresponding optimized geometries? I can supply the input file if needed. Thanks, Chona