[gmx-users] Free energy change and volume of the box

[Alex]

Dear gromacs user,

As you know the binding free energy is the difference between the free
energy change inbounded state and unbounded state.

\Delta (\Delta G)_(binding) = \Delta G_(bounded)  - \Delta G_(unbounded).

Then my question is that if it is necessary to simulate the free energy
change of bonded and unbounded states in the identical volume size?

In another meaning if the free energy change (either bounded or unbounded)
is a volume depended quantity?

I am using FEP method to calculate the binding free energy of amino acid
to  a solid surface.

Best regards,
Alex