The hydrated electron has long served as a paradigm system for connecting the predictions of quantum simulations with experiment.  The structure of the hydrated electron, however, has been the subject of much recent controversy:  the traditional picture is that the hydrated electron resides in a cavity, locally expelling the water, but more recent simulations suggest that a non-cavity structure, where the electron's wavefunction encompasses several water molecules, may be more consistent with experiment.  Related are a whole host of experiments measuing the binding energy of excess electrons to small water clusters, where multiple binding motifs are observed.  In this talk, we work to bridge the gap between the binding energy of water anion clusters and the structure of the hydrated electron in the bulk room temperature liquid by performing ab initio molecular dynamics (MD) simulations of water anion clusters as a function of size.  For our simulations, we chose the BNL range-separated functional, with D3 dispersion correction, as this particular combination has been shown to do an excellent job reproducting the binding energies of a variety of chemical systems.  After careful turning of the range-separation parameter, our MD simulations allow us to study how the binding energy fluctuates with the water dynamics in water anion clusters with different sizes.  We find that there are indeed multiple electron binding motifs with different binding energies, and quenching of configurations gives an excellent explanation of the binding energies observed in the cluster anion photoelectron spectroscopy experiments.  We also see that even though the electron tends to have significant amplitude away from the surface of the smaller clusters, the electron's charge density inside the clusters has significant overlap with multiple water molecules, reminiscent of the non-cavity picture of the bulk hydrated electron.

Towards an Ab initio understanding of the hydrated electron: DFT-based molecular dynamics simulations of water anion clusters

255th National Meeting (2018)

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