Abstract: A method and system for calculating the free energy difference between a target state and a reference state. The method includes determining one or more intermediate states using a coupling parameter, performing molecular simulations to obtain ensembles of micro-states for each of the system states, and calculating the free energy difference by an analysis of the ensembles of micro-states of the system states. The method can be particularly suited for calculating physical or non-physical transformation of molecular systems such as ring-opening, ring-closing, and other transformations involving bond breaking and/or formation. A soft bond potential dependent on a bond stretching component of the coupling parameter and different from the conventional harmonic potential is used in the molecular simulations of the system states for the bond being broken or formed during the transformation.

Abstract: Methods of calculating a free energy of solubility for a compound in a solvent by computer operations include the following steps: (i) establishing, using a computer model, an initial state for a system including an aggregate of multiple molecules of the compound in a solvent; (ii) establishing, using the computer model, a final state of the system including a single molecule from the aggregate fully solvated in the solvent and separate from a transformed aggregate; (iii) transforming, using the computer model, the system from the initial state to the final state, via removing a first molecule of the compound from the aggregate to form the transformed aggregate and replacing the first molecule with solvent at the site of the first molecule; and (iv) calculating the free energy of the transformation between the initial and the final states, which determines the free energy of solubility for the compound.

Abstract: Methods of calculating a free energy of solubility for a compound in a solvent by computer operations include the following steps: (i) establishing, using a computer model, an initial state for a system including an aggregate of multiple molecules of the compound in a solvent; (ii) establishing, using the computer model, a final state of the system including a single molecule from the aggregate fully solvated in the solvent and separate from a transformed aggregate; (iii) transforming, using the computer model, the system from the initial state to the final state, via removing a first molecule of the compound from the aggregate to form the transformed aggregate and replacing the first molecule with solvent at the site of the first molecule; and (iv) calculating the free energy of the transformation between the initial and the final states, which determines the free energy of solubility for the compound.