The 6th International Conference on Matter and Radiation at Extremes (ICMRE2023)

263 / 2023-04-23 16:05:44

A new computational method to apply pressure to molecular systems and its applications to high-pressure organic reactions

High Pressure Physics and Materials Science > Transitions

Pressure is as fundamental as temperature to chemical reactivity. Understanding and controlling organic reactivity under pressure is essential in many areas of high-pressure research and industry, such as the Haber-Bosch process for nitrogen fixation (0.1 kbar; 1 kbar ≈ 1000 atm), prebiotic chemistry under pressure (<1 kbar), diamond synthesis (60 kbar), nanothread synthesis (200 kbar). A challenge in the computational study of high-pressure reactions (especially organic reactions in solution) is to properly incorporate the effect of pressure in electronic structure calculations. The recently-developed eXtreme Pressure-Polarizable Continuum Model (XP-PCM) introduces pressure in the calculation of solvated molecular systems by constraining the accessible space of the molecule’s electrons with a density-dependent repulsive potential around the molecule [1]. The effect of pressure is modeled as a simultaneous increase in the Pauli repulsion between the molecule and the medium and a decrease in the volume of the cavity that accommodates the molecule. The pressure is computed as the derivative of the electronic energy with respect to the cavity volume. The XP-PCM method can be applied to molecular systems without the need for periodic boundary condition.



XP-PCM has been applied to pericyclic reactions under pressure, where interesting phenomena, such as transition state (TS) shifting along the reaction coordinate, conformational change becoming rate-determining, and possible TS turning into a minimum have been revealed [1]. The evolution of the cavity volume throughout the course of the reaction emerges as a useful diagnostic for analyzing the effect of the pressure on the reaction profiles [1,2,3]. Accurate computation of activation volumes by XP-PCM has been shown to be a powerful tool in deciphering competing reaction mechanisms [2]. The partitioning of activation volume into physically meaningful components provides a new and extremely useful way to understand the origin of activation volume [2].



[1] B. Chen, R. Hoffmann, R. Cammi, Angew. Chem. Int. Ed. 56, 11126 (2017).

[2] B. Chen, K. N. Houk, R. Cammi, Chem. Eur. J. 28, e202200246 (2022).

[3] B. Chen, V. H. Crespi, R. Hoffmann, J. Am. Chem. Soc. 144, 9044-9056 (2022).