Empirically Optimized One-Electron Pseudopotential for the Hydrated Electron: A Proof-of-Concept Study

Mixed quantum-classical molecular dynamics simulationshave beenimportant tools for studying the hydrated electron. They generallyuse a one-electron pseudopotential to describe the interactions ofan electron with the water molecules. This approximation shows boththe strength and weakness of the approach. On the one hand, it enablesextensive statistical sampling and large system sizes that are notpossible with more accurate ab initio molecular dynamicsmethods. On the other hand, there has (justifiably) been much debateabout the ability of pseudopotentials to accurately and quantitativelydescribe the hydrated electron properties. These pseudopotentialshave largely been derived by fitting them to ab initio calculations of an electron interacting with a single water molecule.In this paper, we present a proof-of-concept demonstration of an alternativeapproach in which the pseudopotential parameters are determined byoptimizing them to reproduce key experimental properties. Specifically,we develop a new pseudopotential, using the existing TBOpt model asa starting point, which correctly describes the hydrated electronvertical detachment energy and radius of gyration. In addition tothese properties, this empirically optimized model displays a significantlymodified solvation structure, which improves, for example, the predictionof the partial molar volume.

Automated summary

Mixed quantum-classical molecular dynamics simulations are important tools for studying the hydrated electron. They generally use a one-electron pseudopotential to describe the interactions with water molecules. However, there has been debate about the accuracy of these pseudopotentials in describing the properties of the hydrated electron. In this paper, the authors present an alternative approach where the pseudopotential parameters are optimized to reproduce key experimental properties, resulting in improved predictions of various properties.