The path is represented in Fig. , in which only a few ammonia molecules were shown for clarity. Following the path A to D, the starting state is the free CO 2 dissolved in liquid The chemical potential of CO 2 in liquid ammonia is computed in two steps. First, the free energy to introduce a CO 2 molecule from air to liquid ammonia is evaluated using a hybrid Grand Canonical Monte Carlo (GCMC) and molecular dynamics approach. CO 2 is assumed to behave ideally in the gas phase, and this ideal gas reservoir has approximately the same CO 2 partial pressure as the one in air at ambient conditions (≈ 0.4 mbar). Only one CO 2 molecule was inserted or deleted per simulation cell, and no chemical reaction between CO 2 and NH 3 occurred due to the 20 kJ/mol free energy barrier needed to trigger this reaction.