title: Equilibrium properties of the reaction H2 ⇌ 2H by classical molecular dynamics simulations.
abstract: We have developed a classical molecular dynamics model for the hydrogen dissociation reaction, containing two- and three-particle potentials derived by Kohen, Tully and Stillinger. Two fluid densities were investigated for a wide range of temperatures, and 11 fluid densities were considered for one temperature. We report the temperature range where the degree of reaction is significant, and also where a stable molecule dominates the population in the energy landscape. The three-particle potential, which is essential for the reaction model and seldom studied, together with the two-particle interaction lead to a large effective excluded volume diameter of the molecules in the molecular fluid. The three-particle interaction was also found to give a large positive contribution to the pressure of the reacting mixture at high density and/or low temperatures. From knowledge of the dissociation constant of the reaction and the fluid pressure, we estimated the standard enthalpy of the dissociation reaction to be 430 kJ mol(-1) (ρ = 0.0695 g cm(-3)) and 380 kJ mol(-1) (ρ = 0.0191 g cm(-3)). These values are in good agreement with the experimental vaule of 436 kJ mol(-1) under ambient pressure. The model is consistent with a Lennard-Jones model of the molecular fluid, and may facilitate studies of the impact of chemical reactions on transport systems.
authors.affiliation: Norwegian University of Science and Technology, Høgskoleringen 5, 7149 Trondheim, Norway. signe.kjelstrup@ntnu.no.
authors.forename: Ragnhild
authors.initials: R
authors.lastname: Skorpa
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Simon
authors.forename: Dick
authors.initials: D
authors.lastname: Bedeaux
authors.forename: Signe
authors.initials: S
authors.lastname: Kjelstrup