Re: CCL:Temperature fluctuation during a const T simulation

Dear Mike and CCLers,
 The temperature fluctuaction in the NVE ensemble is
 <delta T^2>/T^2=2/3N,
 where N is the number of atoms in your simulation. Check if your variance
 sqrt(<delta T^2>)=50 K is in agreement with this formula. If it is, you
 should increase N, or increase the simulation time, or run several
 paralell simulations with independent initial configurations and average
 them.
 If you receive other answers, please, let know them.
 Regards,
 Eduardo
 On Fri, 25 May 2001, mike smith wrote:
 > Dear listers,
 >
 > In molecular dynamics, there are a lot of techniques
 > to keep the Temperature(T) constant, such as velocity
 > scaling, NOSE heat bath, Langevin dynamics, and so on.
 >
 > However, as you know that the T can't always be a
 > constant, but fluctuating around the input value.
 >
 > I am doing a simulation by Langevin dynamics, and my
 > trouble is that the T fluctuation of my results is
 > very big (The variance of T is about 50K). I think
 > this will weaken any of my conclusions based on the
 > simulation, especially for those temperature senstive
 > quantuties.
 >
 > Since I don't have much experience on Langevin
 > dynamics, I am wondering if anyone could give me some
 > help on how to MINIMIZE the temperature fluctuation
 > for Langevin dynamics. Thanks a lot in advance.
 >
 > Sincerely,
 >
 > Mike Smith
 >
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  Eduardo Ariel Menendez Proupin, Ph.D.
  -------------------------------------
  Laboratorio de Ingenieria de Zeolitas
  Instituto de Materiales y Reactivos
  Universidad de La Habana
  San Lazaro y L.
  Vedado 10400
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  E-mail:eariel ^at^ raman.ff.oc.uh.cu
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