Rendiconti Lincei-Scienze Fisiche E Naturali最新文献

Experimental, theoretical and computational chemical kinetics contribute to progress both in molecular and materials sciences and in biochemistry, exploring the gap between elementary processes and complex systems. Stationary state quantum mechanics and statistical thermodynamics provide interpretive tools and instruments for classical molecular dynamics simulations for stable or metastable structures and near-equilibrium situations. Chemical reaction kinetics plays a key role at the mesoscales: time-dependent and evolution problems are typically tackled phenomenologically, and reactions through intermediates and transition states need be investigated and modelled. In this paper, scaling and renormalization procedures are developed beyond the Arrhenius equation and the Transition State Theory, regarding two key observables in reaction kinetics, the rate “constant” as a function of temperature (and its reciprocal, the generalised lifetime), and the apparent activation energy (and its reciprocal, the transitivity function). Coupled first-order equations—dependent on time and on temperature—are formulated in alternative coupling scheme they link experimental results to effective modelling, or vice versa molecular dynamics simulations to predictions. The passage from thermal to tunnelling regimes is uniformly treated and applied to converged quantum mechanical calculations of rate constants available for the prototypical three-atom reactions of fluorine atoms with both H₂ and HD: these are exothermic processes dominated by moderate tunnel, needing formal extension to cover the low-temperature regime where aspects of universal behaviour are shown to emerge. The results that have been validated towards experimental information in the 10–350 K temperature range, document the complexity of commonly considered “elementary” chemical reactions: they are relevant for modelling atmospheric and astrophysical environments. Perspectives are indicated of advances towards other types of transitions and to a global generality of processes of interest in applied chemical kinetics in biophysics and in astrochemistry.

In the last 50 years, the impressive results on chemical kinetics from crossed molecular beam experiments have been assisted by theoretical and particularly computational progress, among which are: (1) the design and implementation of the SIMBEX (SImulation of Molecular Beam EXperiments) procedure on parallel and distributed computers aimed at rationalizing the dynamical behavior of the investigated systems on the ab initio computed molecular interactions; (2) the establishing of theoretical and computational research and educational networks (like the Quantum Reactive Scattering and European Chemistry Thematic Network), the assembling of virtual research communities (like the meta- and the grid-chemistry ones within the Collaboration in Science and Technology (COST) initiatives to enhance synergic and cooperative work levering on highly productive platforms; (3) the participation in the management of both the Italian and the European grid infrastructures initiatives; (4) the development of molecular open science-enabled cloud services within the European Open Science Cloud (EOSC). Levering on the mentioned collaborative efforts, important open science initiatives have been implemented. The present paper illustrates a prototype model apparatus for the production of methane out of CO₂ using renewable energy sources and a prosumer (producer–consumer) model for delivering online chemistry competence tests. Finally, a suggestion is made to establish networked local services of the academy for high school education.