Subject: Response to MD with variable temp question

From: <[email-masked]>
Date: Tue, 23 Nov 1993 09:05 EST

K. T. Noy writes:

> Subj:	Molecular Dynamics questions

> Dear CCL fellows, 
> 	I am writing an MD program and here comes some questions.
>	To my experience, the average temperature tends to raise
> up gradually in a simulation resulting in the increasing of total
> energy. 

>        1) Is it possible to apply a "scaling temperature" algorithm
> to control the temperature range ( my MD is NVE )
	
>	Thanks a lot in advance.
>						best wishes,
>						T.K.Noy
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I have a comment that is a "tangental" answer. In fitting several 
variable temperature NMR simulations where you have an equilbrium
situation between several species of various populations, I noted 
that I could not obtain satisfactory fits of my spectra by simply 
increasing the rate of exchange between the various species (as 
dictated by the Eyring equation) until I began to increase the 
populations of the minor species with increasing temperature. 

Further, the best fits were obtained when I could track the 
popolations of each species at several temperatures and generate
a Van't Hoff plot that could be used to "predict" the populations
for spectra where overlap prevented population elucidation. 

If your MD model is varying in temperature, a more realistic 
model would include an increasing of minor conformation populations
with increasing temperature (as dictated by the Van't Hoff equation).

What do others think.

Jay Brown