[gmx-users] Free energy change

[Alex]

Dear gromacs user,

I have calculated the free energy change of a charged molecule in box1, but
now, I need to do it again but in a bigger box.

Box1: (a1, b1, c1) and number of water molecules: N1
Box2: (a2, b2, c2) and number of water molecules: N2

To avoid the second simulation, I was wondering how I can have the free
energy change in the second box using the one from the first one?

Unlike to a neutral molecule, the free energy change of a charged molecule
is volume size dependent.

Thanks,
Regards,
Alex