[gmx-users] System size and minimum image convention

[Justin Lemkul]

On 2/21/13 6:10 PM, Elisabeth wrote:
> Hello everyone,
>
> Does anyone know if the minimum image convention has something to do with
> the box size effect (independence of simulation results from system size) ?
> i.e. When the box size is larger than 2*r_c, does this ensure that the
> results are independent of size pf the system (number of atoms in box)?
>
> Please guide me if I am confusing these two issues with each other,
>

The finite size effect and minimum image convention are different.  The minimum 
image convention simply says that your molecules should not have their forces 
double-counted through interactions in the central unit cell and a neighboring 
one.  That leads to spurious dynamics.  A box of 2*r_c is an absolute minimum, 
but if there is a solute involved (i.e. not pure solvent) then your box must be 
larger (diameter of solute + 2*r_c).

-Justin

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

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