We have performed Monte Carlo simulations of the Ag+ cation and of the Ag atom in water. We have used the Kozack and Jordan polarizable water potential. The pairwise solute−water potentials and the three-body cation−water potential are based on MP2 calculations. We get for the hydration enthalpy of Ag+ the value −5.65 ± 0.15 eV, in good agreement with the experimental value: −5.5 ± 0.1 eV. For the ionization free energy of Ag, we have tested three available methods (thermodynamic perturbation, overlapping distribution, and self-consistent histograms methods) and found out that they yield very close results. The redox potential of the Ag+/Ag couple is estimated to be −2.3 V/NHE. Since our potentials include no empirical data, the agreement with the electrochemical value, −1.9 V/NHE, and the thermochemical value, −2.1 V/NHE, is satisfactory.

In this work, we used simultaneously the reaction ensemble Monte Carlo (ReMC) method and the adaptive Erpenbeck equation of state (AE-EOS) method to directly calculate the thermodynamic and chemical equilibria of mixtures of detonation products on the Hugoniot curve. The ReMC method [W. R. Smith and B. Triska, J. Chem. Phys. 100, 3019 (1994)] allows us to reach the chemical equilibrium of a reacting mixture, and the AE-EOS method [J. J. Erpenbeck, Phys. Rev. A 46, 6406 (1992)] constrains the system to satisfy the Hugoniot relation. Once the Hugoniot curve of the detonation product mixture is established, the Chapman-Jouguet (CJ) state of the explosive can be determined. A NPT simulation at P(CJ) and T(CJ) is then performed in order to calculate direct thermodynamic properties and the following derivative properties of the system using a fluctuation method: calorific capacities, sound velocity, and Gruneisen coefficient. As the chemical composition fluctuates, and the number of particles is not necessarily constant in this ensemble, a fluctuation formula has been developed to take into account the fluctuations of mole number and composition. This type of calculation has been applied to several usual energetic materials: nitromethane, tetranitromethane, hexanitroethane, PETN, and RDX.