[gmx-users] energy terms vs. temperature

[Justin A. Lemkul]

Juliette N. wrote:
> 
> 
> On 6 September 2011 15:03, Justin A. Lemkul <jalemkul at vt.edu 
> <mailto:jalemkul at vt.edu>> wrote:
> 
> 
> 
>     Juliette N. wrote:
> 
>         Dear users,
> 
>         I have a short question about temperature dependence of enregy
>         terms i.e bonds, angles, torsions, vdw , electorstatics. I am
>         curious why these energies increase with T. Especially bonded
>         terms that have no temperature dependence in the functional form
>         ( force constants), why all bonded energy terms are increasing
>         with T?
> 
> 
>     I assume you're not using constraints?  Higher temperature induces
>     bond excitation.  Atoms move faster with increasing T, hence kinetic
>     energy influencs bonded terms.
> 
> 
>     Thank you. There are no constraints.  At high T atoms move faster 
> but can you please describe a little more why higher velocity leads to 
> higher non bonded energies between particles? As for bonded terms, is 

Probably because they are more likely to collide and/or come in closer contact.

> that correct to say higher velocities is equivalent to larger deviations 
> from equilibrium state of bonds, angles and dihedrals leasing to higher 
> potential energies?
> 

It's all about competing forces.  Atoms have higher kinetic energy at higher 
temperature and so they can move faster.  Bonds work in opposition to atoms 
moving apart, so yes, there is some larger degree of deviation at higher T.

-Justin

> Thanks,
> 
> 
>     -Justin
> 
>     -- 
>     ==============================__==========
> 
>     Justin A. Lemkul
>     Ph.D. Candidate
>     ICTAS Doctoral Scholar
>     MILES-IGERT Trainee
>     Department of Biochemistry
>     Virginia Tech
>     Blacksburg, VA
>     jalemkul[at]vt.edu <http://vt.edu> | (540) 231-9080
>     <tel:%28540%29%20231-9080>
>     http://www.bevanlab.biochem.__vt.edu/Pages/Personal/justin
>     <http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin>
> 
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> 
> -- 
> Thanks,
> J. N.
> 

-- 
========================================

Justin A. Lemkul
Ph.D. Candidate
ICTAS Doctoral Scholar
MILES-IGERT Trainee
Department of Biochemistry
Virginia Tech
Blacksburg, VA
jalemkul[at]vt.edu | (540) 231-9080
http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin

========================================