Molecular dynamics simulation for chemically reactive substances. Fluorine

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Abstract
Molecular dynamics computer simulation has been utilized to study physical and chemical properties of the highly reactive element fluorine in its fluid phases. The underlying model approximates the energy of the ground electronic state for an arbitrary collection of fluorine atoms with a combination of two and three atom interactions. The classical simulation employed 1000 atoms subject to periodic boundary conditions. Diatomic molecules spontaneously form and are stable at low temperatures, but dissociation and atom exchange reactions occur at high temperatures. Steepest‐descent quenching on the potential energy hypersurface reveals the presence of a temperature‐independent inherent structure for the low‐temperature undissociated liquid. Dissociation is found to be strongly enhanced at high density owing to relatively strong solvation by diatomics of chemically unbonded fluorine atoms. Slow cooling of the fluid from well above the critical temperature, at one‐eighth of the triple‐point density, produced a condensation phenomenon driven by the weak van der Waals attractions that operate between intact diatomic molecules.