Solvation Free Energies from Subsystem Density Functional Theory with Sampling скачать в хорошем качестве

Solvation Free Energies from Subsystem Density Functional Theory with Sampling

Solvation effects on chemical processes in the condensed phase are critical for chemical reactivity. The scope of available strategies attempting to describe such effects reflect their importance; they comprise, e.g., implicit continuum solvation, molecular dynamic simulations, and explicit quantum mechanical description of solute-solvent interactions within a continuum model. The former lacks description of directed interactions, whereas the latter two are either computationally costly or exposed to biased assumptions on the local solvent orientation. Here, we present a new hybrid ansatz using subsystem density functional theory and a conductor-like polarizable continuum model to quantify solute-solvent interactions. To determine the solvation energies, different sampling approaches are analyzed and compared. These include static sampling where configurations are obtained from incremental and systematical addition of solvent molecules to a solute-solvent complex and dynamic sampling where configurations are taken as snapshots from a molecular dynamic simulation. Both are performed in an automatic and systematic fashion, eliminating any bias concerning the local solvation environment of the solute. The sampling approaches allow for error estimation of the mean solvation energies of an ensemble of configurations which is usually not by default included in implicit solvation approaches. We evaluate the quality of our hybrid ansatz and the sampling approaches by comparing calculated activation barriers of reactions in different solvents to experimental results and implicit approaches.