The entropic origin of the enhancement of liquid diffusion close to a neutral confining surface.

It is known that, in the proximity of a neutral wall, liquids experience diffusion enhancement relative to their bulk diffusion, but the origin of this phenomenon is still unknown. We report a molecular dynamics simulation investigating the dynamics of a simple liquid in the proximity to a non-interacting smooth confining wall, which exhibits a strong diffusion enhancement within the liquid layers adjacent to the wall. We present an analysis of these results, demonstrating that the observed diffusion enhancement can be accounted for, with numerical accuracy, using the universal scaling law that relates the liquid diffusion rate to the excess entropy.

A polarizable valence electron density based force field for high-energy interactions between atoms and molecules.

High-accuracy molecular force field models suited for hot gases and plasmas are not as abundant as those geared toward ambient pressure and temperature conditions. Here, we present an improved version of our previous electron-density based force field model that can now account for polarization effects by adjusting the atomic valence electron contributions to match ab initio calculated Mulliken partial charges. Using a slightly modified version of the Hohenberg-Kohn theorem, we also include an improved theoretical formulation of our model when applied to systems with degenerate ground states.

Adsorption of Glycine on TiO in Water from On-the-fly Free-Energy Calculations and In Situ Electrochemical Impedance Spectroscopy.

We report here an experimental-computational study of hydrated TiO anatase nanoparticles interacting with glycine, where we obtain quantitative agreement of the measured adsorption free energies. Ab initio simulations are performed within the tight binding and density functional theory in combination with enhanced free-energy sampling techniques, which exploit the thermodynamic integration of the unbiased mean forces collected on-the-fly along the molecular dynamics trajectories. The experiments adopt a new and efficient setup for electrochemical impedance spectroscopy measurements based on portable screen-printed gold electrodes, which allows fast and in situ signal assessment.

A Simple Electron-Density Based Force Field Model for High-Energy Interactions between Atoms and Molecules.

In high-energy molecular dynamics or Monte Carlo simulations, standard force fields optimized for simulations at ambient temperatures are inadequate. This is largely because their repulsive parts have been regarded as not very significant, even well below zero interaction energies. It is, therefore, not obvious which force fields to resort to for simulating hot gases or plasmas.

Evolutionary Monte Carlo of QM Properties in Chemical Space: Electrolyte Design.

Optimizing a target function over the space of organic molecules is an important problem appearing in many fields of applied science but also a very difficult one due to the vast number of possible molecular systems. We propose an evolutionary Monte Carlo algorithm for solving such problems which is capable of straightforwardly tuning both exploration and exploitation characteristics of an optimization procedure while retaining favorable properties of genetic algorithms. The method, dubbed MOSAiCS (etropolis ptimization by ampling daptively n hemical pace), is tested on problems related to optimizing components of battery electrolytes, namely, minimizing solvation energy in water or maximizing dipole moment while enforcing a lower bound on the HOMO-LUMO gap; optimization was carried out over sets of molecular graphs inspired by QM9 and Electrolyte Genome Project (EGP) data sets.