  In models of Pt 111 and Pt 100 surfaces in water, motions of molecules in the
first hydration layer are spatially and temporally correlated. To interpret
these collective motions, we apply quantitative measures of dynamic
heterogeneity that are standard tools for considering glassy systems.
Specifically, we carry out an analysis in terms of mobility fields and
distributions of persistence times and exchange times. In so doing, we show
that dynamics in these systems is facilitated by transient disorder in
frustrated two-dimensional hydrogen bonding networks. The frustration is the
result of unfavorable geometry imposed by strong metal-water bonding. The
geometry depends upon the structure of the underlying metal surface. Dynamic
heterogeneity of water on the Pt 111 surface is therefore qualitatively
different than that for water on the Pt 100 surface. In both cases, statistics
of this adlayer dynamic heterogeneity responds asymmetrically to applied
voltage.
