Competing Nuclear Quantum Effects and Hydrogen-Bond Jumps in Hydrated Kaolinite

Recent work has shown that the dynamics of hydrogen bonds
in pure
clays are affected by nuclear quantum fluctuations, with different
effects for the hydrogen bonds holding different layers of the clay
together and for those within the same layer. At the clay–water
interface there is an even wider range of types of hydrogen bond,
suggesting that the quantum effects may be yet more varied. We apply
classical and thermostated ring polymer molecular dynamics simulations
to show that nuclear quantum effects accelerate hydrogen-bond dynamics
to varying degrees. By interpreting the results in terms of the extended
jump model of hydrogen-bond switching, we can understand the origins
of these effects in terms of changes in the quantum kinetic energy
of hydrogen atoms during an exchange. We also show that the extended
jump mechanism is applicable not only to the hydrogen bonds involving
water, but also those internal to the clay.