Structure of the water trimer at the magnetite(001) SCV interface

Determine the equilibrium structure of a water trimer adsorbed on the Subsurface Cation Vacancy (SCV) reconstruction of the magnetite (001) surface, clarifying whether the linear or triangular trimer geometry is realized under typical experimental conditions, given that density functional theory calculations indicate equal adsorption energies for both geometries.

Background

Water adsorption on the Subsurface Cation Vacancy (SCV) reconstruction of the magnetite (001) surface forms partially dissociated clusters whose structures depend sensitively on coverage and local environment. Prior experimental observations reported only linear water trimers, whereas density functional theory (DFT) calculations suggested that linear and triangular trimers have comparable adsorption energies. This discrepancy between experimental observation and theoretical prediction motivates a precise determination of the trimer structure under interfacial conditions.

The paper employs a Behler-Parrinello neural network potential to simulate trimer dynamics on the SCV surface, providing statistical evidence that linear trimers are far more probable at 300 K. Nonetheless, the explicitly stated open question concerns establishing the actual structure of the water trimer given the apparent degeneracy in DFT energetics.