Re: add counterions

From: Bill Ross <ross_at_cgl.ucsf.edu>
Date: Wed 30 May 2001 09:58:53 -0700 (PDT)

> solvatebox x WATBOX216 8
> addions x Cl- 0
        
        the box size is 30*30*30A, containing 500 TIP3P waters.
        
> addions x Cl- 0
> solvatebox x WATBOX216 8
        
        the box size is 38*38*38 A, containing 1100 TIP3P waters.
        
        Would you please tell me why a so big difference?

When you solvate before ions are added, the solute is smaller.
After the ions are added in vacuum, the solute is bigger, so
solvating to the same (8A) distance necessitates a larger box.

8A is a small box clearance to use when solvating before addions.
Solvating before addions provides better packing of the box, because
in this case addions replaces the nearest water when an ion position
overlaps.

Bill Ross
Received on Wed May 30 2001 - 09:58:53 PDT
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