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Computing accurate rate constants for catalytic events occurring at the surface of a given material represents a challenging task with multiple potential applications in chemistry. To address this question, we propose an approach based on a combination of the rare event sampling method called adaptive multilevel splitting (AMS) and ab initiomolecular dynamics. The AMS method requires a one-dimensional reaction coordinate to index the progress of the transition. Identifying a good reaction coordinate is difficult, especially for high dimensional problems such as those encountered in catalysis. We probe various approaches to build reaction coordinates such as support vector machine and path collective variables. The AMS is implemented so as to communicate with a density functional theory-plane wave code. A relevant case study in catalysis, the change of conformation and the dissociation of a water molecule chemisorbed on the (100) γ-alumina surface, is used to evaluate our approach. The calculated rate constants and transition mechanisms are discussed and compared to those obtained by a conventional static approach based on the Eyring–Polanyi equation with harmonic approximation. It is revealed that the AMS method may provide rate constants that are smaller than those provided by the static approach by up to 2 orders of magnitude due to entropic effects involved in the chemisorbed water molecule.

Transition aluminum oxides, such as γ-Al2O3or alumina, are widely used in many different technical applications that rely on the surface reactivity of this material at the solid liquid interface. The speciation of surface sites of this material confronts several obstacles. On the one hand, alumina is a poorly crystalline oxide, thus allowing for a limited amount of empirical structural information for an important number of surface sites with different trends in reactivity and, on the other hand, it is a metastable material. In this work, we show several ways in which the multisite complexation model, combined with atomistic information from density functional theory and ab initio molecular dynamics (AIMD), can manage to perform speciation calculations of γ-Al2O3surface sites at the solid liquid interface. Although the results are in good qualitative agreement with experimental titration curves, and they can serve as a guide for the interpretation of the reactivity of this material at the initial stages of an impregnation experiment and chemical weathering phenomena, this work highlights the need of more complex AIMD simulations to accurately model these phenomena in γ-Al2O3surface/liquid interfaces.

Solid sulfide electrolytes hold great promise for making all-solid state batteries a reality. Therefore, their wet chemical synthesis has become increasingly important in recent years due to various benefits such as scalability and versatility. The Li3PS4electrolyte has a relatively high ionic conductivity (≈10–4S cm–1at 25 °C) and can be synthesized in various organic solvents by reacting Li2S and P2S5. It is well-known that the choice of the solvent is critical for the synthesis. Herein, we investigated several new organic polar solvents such as sulfur-based solvents (propanethiol, thiolane, and thiophene), amines, and carbonyls (esters, carbonates, ketones) for the synthesis of Li3PS4. The relationship between the ability to perform the reaction, the ionic conductivity, and the solvents’ characteristics revealed that the electronic density of the polar function plays a key role. The results of this study can be used as a guideline to select new synthesis solvents. We also identify a particular solvent, isobutyl isobutyrate (IBIB), which allows the decomposition of the corresponding Li3PS4solvato-complex below the boiling point of the solvent with one of the highest reported ionic conductivities for the wet chemical method (2.1 × 10–4S cm–1at room temperature).