In a solid catalyst with ionic liquid layer (SCILL), ionic liquid (IL) coatings are used to improve the selectivity of noble metal catalysts. To understand the origins of this selectivity control, we performed model studies by surface science methods in ultrahigh vacuum (UHV). We investigated the growth and thermal stability of ultrathin IL films by infrared reflection absorption spectroscopy (IRAS). We combined these experiments with scanning tunneling microscopy (STM) to obtain information on the orientation of the ions, the interactions with the surface, the intermolecular interactions, and the structure formation. Additionally, we performed DFT calculations and molecular dynamics (MD) simulations to interpret the experimental data. We studied the IL 1‐ethyl‐3‐methylimidazolium trifluoromethanesulfonate [C2C1Im][OTf] on Au(111) surfaces. We observe a weakly bound multilayer of [C2C1Im][OTf], which is stable up to 390 K, while the monolayer desorbs at ∼450 K. [C2C1Im][OTf] preferentially adsorbs at the step edges and elbows of the herringbone reconstruction of Au(111). The anion adsorbs via the SO3 group with the molecular axis perpendicular to the surface. At low coverage, the [C2C1Im][OTf] crystallizes in a glass‐like 2D phase with short‐range order. At higher coverage, we observe a phase transition to a 6‐membered ring structure with long‐range order.

A new method for constructing a full-dimensional potential energy surface representation in black-box fashion for an arbitrary reaction is presented. With limited knowledge of the system and with a limited number of reference-level data points, it is possible to calculate reaction rate constants with high quality. Building on our recently published application of Grimme’s quantum-mechanically derived force field (QMDFF) and its empirical valence bond extension EVB-QMDFF to rate constant calculations, an improved EVB coupling method with local corrections was developed in order to avoid spurious problems for certain systems and hence to achieve an even wider range of applicability. A given reaction path (RP) is modeled as a parametric curve via cubic spline interpolation; regions offside this path are then extrapolated with quadratic Taylor series, and regions around the transition state are corrected by introduction of direct reference interpolation; the method is named transition region corrected RP-EVB-QMDFF (TREQ). To verify the quality of TREQ, six reactions were chosen for which full-dimensional analytical potential surfaces are available in the literature. Chemical reaction rates were calculated with ring polymer molecular dynamics on the reference surfaces as well as on the TREQ surfaces resulting in excellent agreement.

Building on the recently published quantum-mechanically derived force field (QMDFF) and its empirical valence bond extension, EVB-QMDFF, it is now possible to generate a reliable potential energy surface for any given elementary reaction step in an essentially black box manner. This requires a limited and pre-defined set of reference data near the reaction path and generates an accurate approximation of the reference potential energy surface, on and off the reaction path. This intermediate representation can be used to generate reaction rate data, with far better accuracy and reliability than with traditional approaches based on transition state theory (TST) or variational extensions thereof (VTST), even if those include sophisticated tunneling corrections. However, the additional expense at the reference level remains very modest. We demonstrate all this for three arbitrarily chosen example reactions.

The initial formation cycles are critical to the performance of a lithium-ion battery (LIB), particularly in the case of silicon anodes, where the high surface area and extreme volume expansion during cycling make silicon susceptible to detrimental side reactions with the electrolyte. The solid electrolyte interface (SEI) that is formed during these initial cycles serves to protect the surface of the anode from a continued reaction with the electrolyte, and its composition reflects the composition of the electrolyte. In this work, ReaxFF reactive force field simulations were used to investigate the interactions between ether-based electrolytes with high LiTFSI salt concentrations (up to 4 mol/L) and a silicon oxide surface. The simulation investigations were verified with galvanostatic testing and post-mortem X-ray photoelectron spectroscopy, revealing that highly concentrated electrolytes resulted in the faster formation and SEIs containing more inorganic and silicon species. This study emphasizes the importance of understanding the link between electrolyte composition and SEI formation. This ReaxFF approach demonstrates an accessible way to tune electrolyte compositions for optimized performance without costly, time-consuming experimentation.

Evaluation of thermochemistry in solution plays a key role in numerous fields. For this task, the solvent effects are commonly included in theoretical computations based on either implicit or explicit solvent approaches. In the present study, we evaluate and compare the performance of some of the most widely applied methods based on these two approaches. For studying the solvent effect on thermochemistry with an explicit solvent, we demonstrate that partial normal mode analysis with frozen geometry of solvent molecules for multiple solute–solvent configurations can yield quite accurate and reliable results for a drastically reduced computational cost. As a case study, we consider the evaluation of the equilibrium constant for the boron isotope exchange between boric acid and borate (k 3–4) in pure and saline water which is of high geochemical importance. Employing three different rigorous and high-precision theoretical approaches, we provide a reliable estimation of k 3–4 which is a value within 1.028 to 1.030 for both pure and saline water which is in excellent agreement with experimental data.