Isotope Effects in Water: Differences of Structure, Dynamics, Spectrum, and Proton Transport between Heavy and Light Water from ReaxFF Reactive Force Field Simulations

Investigating
properties of both heavy and light water at the atomistic
level is essential to understanding chemical and biological processes
in aqueous solution. However, appropriately describing their difference
on the nanoscale is still challenging. Employing ReaxFF reactive molecular
dynamics simulations, we systematically study the structure, dynamics,
and spectra of heavy and light water. With the water force field potential
we developed, the different features between heavy and light water
can be simulated appropriately by the classical treatment on large
size and time scale. Here, we also report the structural difference
between D3O+ and H3O+ in
bulk heavy/light water. In addition, the diffusion constants of heavy
and light water are successfully reproduced, and the Grotthuss hopping
mechanism of proton transport in liquid water is properly described
as well. It allows us to study a complex system in heavy/light aqueous
environments, such as proton transport, chemical reaction, and tracing
the reaction mechanism with an isotope substitute.