From owner-chemistry@ccl.net Tue Nov 25 04:35:01 2008 From: "Lukasz Cwiklik cwiklik-#-gmail.com" To: CCL Subject: CCL:G: van der Waals parameters for Ti Message-Id: <-38169-081125041507-8385-qZ4XzJUqunxVEVxADJqfxA..server.ccl.net> X-Original-From: "Lukasz Cwiklik" Content-Disposition: inline Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=ISO-8859-1 Date: Tue, 25 Nov 2008 11:14:53 +0200 MIME-Version: 1.0 Sent to CCL by: "Lukasz Cwiklik" [cwiklik[]gmail.com] Dear Saurabh, I do not know any tutorial, however, I will try to describe the general procedure. The way to estimate vdW parameters with ab initio (eg. Gaussian) is to scan a potential energy surface for interactions between your atom (rutile) and the atoms/molecules which rutile will interact with in your simulation. In the simples case, if you have just rutile-rutile interactions, make a scan of energy in Gaussian for changing the rutile-rutile distance. Then assume the parameters for rutile (for starters, take radius and well depth for a similar atom) and make the same scan in your MD code. Then the hard part starts - you need to fit (just by hand or write a code) the radius and well depth to have an agreement between ab initio and the empirical energy vs. distance curve (in a range of method's error which sometimes can be as high as 2 kcal/mol). One should remember about the basis set superposition error, however, there is no ideal method to get rid of bsse in this case. Best, Lukasz -- Lukasz Cwiklik http://cwiklik.wordpress.com On Mon, Nov 24, 2008 at 4:02 PM, Saurabh Agrawal Saurabh.Agrawal^^ucdconnect.ie wrote: > > Sent to CCL by: "Saurabh Agrawal" [Saurabh.Agrawal/./ucdconnect.ie] > Dear CCl users, > > I am trying to get non bonded parameters (van der Waals' radius and well depth) for Ti atom (rutile). I appreciate if some one could provide these parameters to me or let me know the way (tutorial) to calculate these parameters using Gaussian. > > Thanking you in advance. > > Best, > > Saurabh Agrawal, > PhD student, > University College Dublin, > Ireland> > >