On Wed, 10 Jan 2007 17:36:10 +1100
 Mark Abraham <[EMAIL PROTECTED]> wrote:
Hu Zhongqiao wrote:
Hi,
Nobody implied me till now. So that means the current version can not do BD by implicitly treating water into continuum media, i.e, use of dielectric constant of water. I hope Gmx developers can help me to make sure this. Till to now I am been using Gmx and in the near future I need to do BD for longer time scale. If Gmx can not help, it will be bad.

GROMACS does not permit implicit solvent models for any of its integration methods. Other simulation packages do.

Mark
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If I am not mistaken implicit solvent is implemented in GMX for using sd integration. (Never did any proteins ;), so don't blame me if I'm wrong.)

The GB82 langevin integrator implemented in gromacs (option "sd" in mdp file) is however a generalized langevin integrator. The BD euler scheme (bd in mdp file), is just a solution of the same differential equation as the SD equation, however now this differential equation can be simplified as some terms (inertia) become insignificant in the limit of high friction.

"Generalized" means that the sd-scheme in gromacs is capable to solve the equations of motions in both the newtonian limit (tau_t >>> 0) as well as in the brownian regime (tau_t -> 0 ). Ofcourse, it can still only handle the friction coefficients in the limits to some numerical extend. If the friction coefficent is reasonable small you will be still able to do brownian dynamics with the sd integrator and use implicit solvent options.

Anyway,

Good luck !!!!!!!

greetings

Jelger

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