Small differences in physical and chemical properties of H2O and D2O, such as melting
and boiling points or pKa, can be traced back a slightly stronger hydrogen bonding
in heavy versus normal water. In particular, deuteration reduces zero-point vibrational
energies as a demonstration of nuclear quantum effects. In principle, computationally
demanding quantum molecular dynamics is required to model such effects. However,
as already demonstrated by Feynmann and Hibbs, zero point vibrations can be effectively
accounted for by modifying the interaction potential within classical dynamics.
In the spirit of the Feymann-Hibbs approach, we develop here two water models for
classical molecular dynamics by fitting experimental differences between H2O and D2O.
We show that a 3-site SPCE-based model accurately reproduces differences between
properties of the two water isotopes, with a 4-site TIP4P-2005/based model in addition
capturing also the absolute values of key properties of heavy water. The present models
are computationally simple enough to allow for extensive simulations of biomolecules
in heavy water relevant, e.g., for experimental techniques such as NMR or neutron
scattering.