[gmx-users] Lambda Dependence when delta_lambda = 0

David spoel at xray.bmc.uu.se
Thu Sep 11 08:26:01 CEST 2003

On Thu, 2003-09-11 at 00:53, Ilya Chorny wrote:
> Hi Erik,
> I ran a short test trajectory where 100 ps calculating the free energy
> of going from Ar - LJ1 (argon with a sigma one Angstrom smaller). In the
> mdp file I set free energy to yes and kept the rest of the free energy 
> parameters as defaults. I'm not sure I understand what the dH/dl in the
> case when delta_lambda = 0. Should it not just be the difference in the
> Hamiltonians between Ar and LJ1. The numbers seem a little high (~7000
> kJ/mol) and I would expect them to be negative. 

dH/dl is the derivative of the energy with respect to lambda, it may
very well be non zero for any value of lambda. I think it is described
in the manual..

> Thanks,
> Ilya
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Groeten, David.
Dr. David van der Spoel, 	Dept. of Cell and Molecular Biology
Husargatan 3, Box 596,  	75124 Uppsala, Sweden
phone:	46 18 471 4205		fax: 46 18 511 755
spoel at xray.bmc.uu.se	spoel at gromacs.org   http://xray.bmc.uu.se/~spoel

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