Improved modeling of electrified interfaces using the effective screening medium method

An update of the effective screening medium (ESM) method [Otani and Sugino, Phys. Rev. B 73, 115407 (2006)] is presented, extending the ability to simulate electrified interfaces in an efficient and flexible way. The need for an artificial vacuum buffer between the molecular system and the screening medium is removed by defining a smooth transition of the ESM dielectric permittivity (smooth ESM), precluding numerical instabilities when molecules come in contact with the ESM. Moreover, at short distances, the smooth ESM acts as a repulsive wall, and thus the simulation cell can serve as a natural container for molecules in molecular-dynamics simulations. Consequently, the smooth ESM method is a substantial advancement in modeling solid-liquid interfaces under electric bias.