Re: Convergence of the Gram-Charlier expansion

From: Ali Khanlarkhani (alikhanlarkhani_at_yahoo.com)
Date: Sun Sep 30 2012 - 12:32:29 CDT

Dear Chris Many thanks, really helpful, in my idea your following sentence, should be added to 'ParseFEP Plugin' manual: "The farthest you are from second-order perturbation theory, the slower the convergence of your Gram-Charlier expansion." regards Ali ________________________________ From: Chris Chipot <chipot_at_ks.uiuc.edu> To: Ali Khanlarkhani <alikhanlarkhani_at_yahoo.com> Cc: "namd-l_at_ks.uiuc.edu" <namd-l_at_ks.uiuc.edu> Sent: Sunday, September 30, 2012 8:16 PM Subject: Re: namd-l: Convergence of the Gram-Charlier expansion Khanlarkhani, you can restate your free energy change, as where g(∆U) is a Gaussian distribution and Hn(∆U) are Hermite polynomials. The farthest you are from second-order perturbation theory, the slower the convergence of your Gram-Charlier expansion. As for the order, it is pretty much system dependent. Charging a van der Waals particle will evidently be pretty quick. Chris Chipot On 9/30/12 5:34 PM, Ali Khanlarkhani wrote: The following sentence come from "ParseFEP Plugin, Version 1.5" manual: > >"Convergence of the Gram-Charlier expansion at a given order represents a relevant measure of how well-defined the probability distribution is." >What does it mean? convergence at what order is good? > >Khanlarkhani > -- _______________________________________________________________________ Chris Chipot, Ph.D. Theoretical and Computational Biophysics Group Beckman Institute University of Illinois at Urbana-Champaign 405 North Mathews Phone: (217) 244-5711 Urbana, Illinois 61801 Fax: (217) 244-6078 E-mail: chipot_at_ks.uiuc.edu Christophe.Chipot_at_edam.uhp-nancy.fr Web: http://www.ks.uiuc.edu/~chipot http://www.edam.uhp-nancy.fr The light shines in the darkness, and the darkness has not overcome it. John 1:5. _______________________________________________________________________

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