[gmx-users] Delta_E´s in TI Method

Mauricio Sica msica at ffyb.uba.ar
Tue Mar 7 14:51:00 CET 2006

Dear all
   I have the following question. I´m doing Delta_G estimations by MD
implementing the Thermodynamic Integration Method (TIM). So I got the
<dG/dl>´s from the simulations and then, the Delta_G by integrating the
curve of <dG/dl> vs. lambda. Ok? Well. Now the problem arise when I
want to get some estimations of the different components contributing
to these Delta_G´s (Coulombic, LJ and so on). (I´ve read the paper of
Mark & van Gunsteren which says that although Delta_G is a state
funtion their contributions are not. But nevertheless I want to take a
glance on this contributions).
   The questions is: I think that I cannot simply substract the average of
lambda=1 to that of lambda=0 (In fact, when I do this for <Protential
energy> what I get is far from the value achieved by the TIM. It´s
obvious?). I think that I should do the integrations of each <dE/dl>
vs. lambda for each contributions. Is it correct? How can I do it?
Thank you in advance

Mauricio Sica
Laboratorio de Expresión y Plegamiento de Proteínas
Uniersidad de Quilmes
Bernal, Buenos Aires

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