Enhancing the configurational sampling of ions in aqueous solution using adiabatic decoupling with translational...

Three methods to enhance the configurational sampling of ions in aqueous solution, temperature and Hamiltonian replica exchange and adiabatic decoupling with translational temperature scaling, were compared for a system of CaSO(4) in water. It took 11 replicas in the case of temperature replica exchange to make use of a diffusion coefficient that is a factor of 1.5 larger at 350 K compared to that at 300 K. Thirty replicas were required in the Hamiltonian replica exchange with charge reduction to reach uncharged ions that have a diffusion coefficient that is 2-7 times larger than the fully charged ones. The adiabatic decoupling technique with translational temperature scaling yielded a diffusion coefficient that was 15 times larger while keeping the distribution of the water molecules around the ions unaltered with respect to the standard temperature simulation. This result illustrates the efficiency of the adiabatic decoupling technique to enhance configurational sampling.