From owner-nwchem-users@emsl.pnl.gov Sun Nov 25 14:44:51 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 lAPMioZC004523 for ; Sun, 25 Nov 2007 14:44:51 -0800 (PST) Received: (from majordom@localhost) by odyssey.emsl.pnl.gov (8.14.1/8.14.1/Submit) id lAPMioOe004522 for nwchem-users-outgoing-0915; Sun, 25 Nov 2007 14:44:50 -0800 (PST) X-Authentication-Warning: odyssey.emsl.pnl.gov: majordom set sender to owner-nwchem-users@emsl.pnl.gov using -f X-Ironport-SG: OK_Domains X-Ironport-SBRS: 3.9 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AgAAAH+JSUdA6aa1lWdsb2JhbACPPwEBAQEHBAQJChYCgQ8 X-IronPort-AV: E=Sophos;i="4.21,464,1188802800"; d="scan'208";a="38205948" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:message-id:date:from:sender:to:subject:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references:x-google-sender-auth; bh=rjt07NgQ4BLmikDCG7LVDeScnI0AHHGWrY4Y/7A2tt4=; b=LcCTdlhsSk4Xu5ZAL8rh0OcYkPubh0+hgMdAzNNXTQmvdmnFbQK/24dqCiRDWcXHXl6JG9+KWC1RP1NVzp4Y9355c6fXdNBtV+YAUiWRsSgsNrBwTM6U6DnJrlkcvMv9fIroTxB2aeLrOBsswyYjj4TXw+saCo1On3cYkkaTMTQ= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=received:message-id:date:from:sender:to:subject:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references:x-google-sender-auth; b=pJIM7ekrGKZhKi/4TDUByQExGGdBjb25OA0MnJ0EpBf678Cz8YA8qrWAFf2D/8p6oJgPhyH2U0ANKUS+UUiiMKw195H97SsLpQ1sej+KuuE1PcfTHmUqPoltMKXkaQQIDR5dZ4zBeo4tjjxPDFfqRiWbeE/o4iAdLPjNCZVjFyk= Message-ID: <809a4c910711251444q3ab1f85eo9dcd51689638df57@mail.gmail.com> Date: Sun, 25 Nov 2007 17:44:47 -0500 From: "Chona S. Guiang" To: "Bylaska, Eric J" , nwchem-users@emsl.pnl.gov Subject: Re: [NWCHEM] questions about PSPW In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <809a4c910711210807j145322f3m44970c82cefa505b@mail.gmail.com> X-Google-Sender-Auth: 2d5345d3acde1274 Sender: owner-nwchem-users@emsl.pnl.gov Precedence: bulk Hi Eric, Thanks for the information on wavefunction_cutoff and energy_cutoff. I'll try adding the former option to my input. Also, I'll go with the automatic grid right now but I'll keep in mind the use of "mapping 2" if I run into problems with the default choice. I'll send a separate email to Patrick to ask for his Ti pseudopotential. Thanks, Chona On Nov 24, 2007 7:35 PM, Bylaska, Eric J wrote: > 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 > 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. > > 2. In general the coordinate doesn't matter if the cutoff energies are > high enough and the system is an insulator. > > 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. > > With the upcoming release, nwchem 5.1, the definition of the cutoff > energy has been simplified. > > 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 >