Re: how to apply a random force on a atom

From: Phoenix (
Date: Tue Jun 07 2005 - 01:08:36 CDT

Thanks for the reply!!
Describe my problem in a simple way: I want to apply a random force on a atom
between a certain range ,for example between 80-100 PN,and I want the
strength of the force random in every step while the direction was fixed,how
to do it??

在 2005年6月7日 星期二 05:06,您写道:
> Hi,
> The Langevin temperature control scheme will do something similar to what
> you are trying to do. You can apply Langevin forces to one or more atoms.
> If I am not mistaken, the random forces have no time correlation and have a
> Gaussian distribution with a mean of zero and a mean squared value that
> depends on the temperature and the damping constant. However, the scheme
> also applies a viscous drag force. Using the Langevin scheme would be less
> work than trying to implement random forces in tcl. It would also guarantee
> that the random forces do not heat up the system. Why do you want to apply
> random forces to one atom?
> Blake
> -----Original Message-----
> From: [] On Behalf
> Of ÎâºéÃ÷ Sent: June 6, 2005 1:32 PM
> To:
> Subject: namd-l: how to apply a random force on a atom
> i am a green hand to namd,now i want to do a simulation withing a random
> force applying on a atom in a peptite in the whole simulation process.For
> example,i want the force random in every step ,not only the size ,but also
> the direction.Is there anyway ??? Can the tclforce meet this require???

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