I am working on a Protein-DNA complex. I run my simulations with Amber14sb-PARMbsc1 force field. We performed couple of simulations to see the difference of using different ions (e.g. Na and K). As can be seen in the figure, we observed an explicit difference between the potential energy values of simulations containing Na and K, regardless of random seed. Do you have any idea why and what could lead us to? Thanks in advance.