The Quantum Chemical Study of Chemical Reactions at Extreme High Pressure by Means of the Extreme-Pressure Polarizable Continuum Model

A new quantum chemical method, XP-PCM, for studying reactive systems at extreme high pressures (p > 1 GPa) is reviewed. The method is an extension of the standard polarizable continuum model, that is, usually used for the description of a molecular solute at a standard condition of pressure and temperature. It introduces the effects of the pressure by means of the increase of the Pauli repulsion interaction between the solute and the environment, which is the dominant component of the intermolecular interactions in dense system at extreme high pressure. The XP-PCM method allows one to build an effective potential energy surface from which the effect of the pressure on the activation energy and the reaction energy can be determined. From this information, the activation and reaction volumes can be estimated. The Diels–Alder dimerization of cyclopentadiene under extremely high pressure is presented as working case.