From owner-chemistry@ccl.net Wed Jul 20 05:44:00 2011 From: "Paul Fleurat-Lessard Paul.Fleurat-Lessard%ens-lyon.fr" To: CCL Subject: CCL:G: software to optimize a large molecule Message-Id: <-45113-110720030951-13153-FZTTgN0XTxTZiNiJgQRmpg=server.ccl.net> X-Original-From: Paul Fleurat-Lessard Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=ISO-8859-1; format=flowed Date: Wed, 20 Jul 2011 09:09:33 +0200 MIME-Version: 1.0 Sent to CCL by: Paul Fleurat-Lessard [Paul.Fleurat-Lessard__ens-lyon.fr] Hi, It seems that you want to use DFT. I think that one option not yet mentionned would be to use a QM:QM' or QM:MM approach. With this hybrid scheme you can use DFT for the metal and its close surrounding and then either a semi-empirical or MM level for the rest of the molecule. Concerning the geometry optimization efficiency, in my experience, Gaussian is really good for this task, but it is not free. In any case, it might be a good option to pre-optimize using a 'low-cost' level such as semi-empirical or MM, and the you can optimize the molecule at the DFT level if you need. Regards, paul. Le 20/07/2011 07:02, psavita(~)crlindia.com a écrit : > Sent to CCL by: psavita() crlindia.com > Hello Neranjan, > > It seems you need to optimize this large molecule having no periodic boundaries. > So it > is going to be compute intensive for any software, whether that employs plane waves > (as in abinit and QE) or Gaussians (GAMESS). For large systems, it may be better > to use > semiempirical (such as MOPAC) or MM (such as GULP) prior to full ab initio > optimization. > On the other hand, if your system is describable with a unit cell with few > atoms, abinit or QE will be very fast. > > Your question may be fully answered if the system is properly understood. > > Best wishes, > > > Savita Pundlik > Computational Materials Applied Research Group > Computational Research Laboratories Ltd., > Taco House, Damle Path, Off Law College Road > Pune - 411004, India. > > > -=his is automatically added to each message by the mailing script =- To recover > the email address of the author of the message, please change the strange > characters on the top line to the -$- sign. You can also look up the > X-Original-From: line in the mail header. E-mail to subscribers: > CHEMISTRY-$-ccl.net or use:E-mail > to administrators: CHEMISTRY-REQUEST-$-ccl.net or useBefore posting, check wait time at: > http://www.ccl.netConferences: > http://server.ccl.net/chemistry/announcements/conferences/ Search Messages: > http://www.ccl.net/chemistry/searchccl/index.shtml If your mail bounces from CCL > with 5.7.1 error, check:RTFI: > http://www.ccl.net/chemistry/aboutccl/instructions/ -- Fleurat-Lessard Paul, Associate Professor Laboratoire de Chimie e-mail: Paul.Fleurat-Lessard-$-ens-lyon.fr Ecole Normale Supérieure de Lyon Tel: + 33 (0)4 72 72 81 54 46, Allée d'Italie Fax: + 33 (0)4 72 72 88 60 69364 Lyon Cedex 07