Author: Edward

Ryan Mullen’s paper on using reaction ensemble Monte Carlo to compute absorption isotherms for CO2 in reactive ionic liquids has appeared in the Journal of Chemical Theory and Computation. In this paper, we show that one can get quantitative agreement with experiment for the absorption of CO2 into an aprotic heterocyclic anion ionic liquid using reaction ensemble Monte Carlo (RxMC) with the semigrand reaction move. Heats of absorption and reaction from both experiment and simulation are exothermic and of comparable magnitude. Replacing experimental Henry’s constants with their simulated counterparts improves the accuracy of a Langmuir-type model at moderate pressures. Nonidealities that affect chemical equilibrium are identified and calculated with high precision.

Our paper entitled “A Molecular Dynamics Investigation Of Actinyl-Ligand Speciation In Aqueous Solution” (Ken Newcomb, Surya Prakash Tiwari, Neeraj Rai^b  and  Edward J. Maginn) was recently published in Physical Chemistry Chemical Physics (DOI: 10.1039/C8CP01944D). In this paper, we use molecular dynamics simulations to calculate the potential of mean force (PMF) between two actinyl ions (UO2 2+ and NpO2 +) and various ligands (F–, Cl-, OH-, NO3-, SO4-2, CO3-2, Na+, and H2O) in explicitly-modeled aqueous solution. Equilibrium constants were calculated from the PMFs, and are consistent with experimental trends. Dication actinyls show stronger affinity for anions compared to monocation actinyls, whereas the opposite is true for cation–cation interactions between actinyls. Finally, the dynamics of actinyl–ligand contact ion pair (CIP) dissociation were characterized by calculating rate constants from transition state theory. The transmission coefficient, a dynamical correction factor used to correct for reaction barrier recrossing, was calculated for each actinyl–ligand CIP dissociation event.

The long-awaited paper describing Cassandra and its features has finally been published (Journal of Computational Chemistry, 2017, 38, 1727-1739).The different features and algorithms used in Cassandra are described, along with implementation details and theoretical underpinnings to various methods used. Benchmark and example calculations are shown, and information on how users can obtain the package and contribute to it are provided. We also made the cover! Please cite this paper if you use Cassandra.