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Abstract

We propose an open-boundary molecular dynamics method in which an atomistic system is in contact with an infinite particle reservoirat constant temperature, volume, and chemical potential. In practice, following the Hamiltonian adaptive resolution strategy, the systemis partitioned into a domain of interest and a reservoir of non-interacting, ideal gas particles. An external potential, applied only in theinterfacial region, balances the excess chemical potential of the system. To ensure that the size of the reservoir is infinite, we introduce aparticle insertion/deletion algorithm to control the density in the ideal gas region. We show that it is possible to study non-equilibriumphenomena with this open-boundary molecular dynamics method. To this aim, we consider a prototypical confined liquid under the influenceof an external constant density gradient. The resulting pressure-driven flow across the atomistic system exhibits a velocity profile consistentwith the corresponding solution of the Navier–Stokes equation. This method conserves, on average, linear momentum and closely resemblesexperimental conditions. Moreover, it can be used to study various direct and indirect out-of-equilibrium conditions in complex molecularsystems.