FIG. 2.
(a) Schematic representation of the alchemical step, exchanging the identities of particles 1 and 2: Particle type 1′ (or 2′) initially is a particle type 1 (or 2) and is modified to particle type 2 (or 1). (b) The change in LJ parameters for the type 1′ and 2′ particles. The εkl grows linearly for k ≠ l and decreases for k = l. (c) The evolution of the parameters during an M trajectory. Note that the work is different from zero only along the purple lines where the positions of the particles are fixed and the interaction parameters are modified. The acceptance or rejection of the MDAS move is based on the value of the work using a Metropolis criterion. The horizontal black lines correspond to δ trajectories.