The pressure or concentration in each of the two control volumes is maintained through periodic exchanges with a reference bulk reservoir. For this, a separate MD simulation of the bulk gas system is performed at specific temperature and pressure of interest. Specifically, in the case of a binary mixture, the reference bulk system consists of 150 CO 2 and 850 N 2 molecules at 1 bar and 308 K, which corresponds to a box of approximately 36×36×36 nm 3 in size. This system is first equilibrated under NPT conditions for 5 ns. This is followed by 1 ns NVT equilibration and 5 ns production run. Out of the 5 ns production run, 5000 frames are extracted. In the DCVMD simulation, a random frame is picked at time intervals defined by the exchange time constant τ . A portion of the system of the same dimensions as the control volume is then selected from the frame, and the current configuration of molecules in the source control volume is replaced by the configuration extracted from the subvolume of the reference bulk system. The new configuration inherits both coordinates and velocities from the parent bulk system. This protocol deviates from the "classical" DCVGCMD approach based on random insertion of molecules in the control volumes and on using the acceptance criteria based on the chemical potential or fugacity. However, the validity of the current protocol, termed here for simplicity Dual Control Volume Molecular Dynamics (DCVMD), has been tested by monitoring the average values of density and composition. The average density must be consistent with the set value of pressure, and the average composition must also be equal to the desired set value. At the same time, this approach avoids the well known pitfalls of the original DCVGCMD, including inefficiency of the insertion attempts and the extended Hamiltonian conservation issues caused by the discontinuous perturbation of the MD trajectories.