A total of 15 different stages were used for the free energy calculations where m = 0 corresponds to a non-interacting (ideal gas) state and m = 14 is a fully interacting system. From m = 1 to 10 the LJ interactions were increased from λ LJ m = 0.1 to 1.0 in 10 equal increments of 0.1. Electrostatic interactions were increased in a square root fashion following λ elec m ={0.50,0.71,0.87,1.00} from m = 11 to 14 . The simulation parameters for the free energy calculations were the same as the last step of equilibration except the equations of motion were integrated with the GROMACS "stochastic dynamics" integrator, corresponding to stochastic or velocity Langevin dynamics integrated with the leap-frog algorithm . The time constant for the stochastic (or Langevin) thermostat was 1.0 ps. This change is necessary as a local thermostat is required to correctly control the temperature of a decoupled and weakly coupled solute molecule.