Heavy Water Models for Classical Molecular Dynamics: Effective Inclusion of Nuclear Quantum Effects

Abstract

Small differences in physical and chemical properties of H 2 O and D 2 O, such as melting and boiling points or pK a , can be traced back to a slightly stronger hydrogen bonding in heavy versus normal water. In particular, deuteration reduces zeropoint 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 H 2 O and D 2 O. We show that a three-site SPCE-based model accurately reproduces differences between properties of the two water isotopes, with a four-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, for example, for experimental techniques such as NMR or neutron scattering.

Anisotropic Electrostatic Interactions in Coarse-Grained Water Models to Enhance the Accuracy and Speed-Up Factor of Mesoscopic Simulations

“…To mitigate the inaccuracies in sampling the higher frequency motions, the mass of CG water molecules is progressively increased as to have a larger moment of inertia and slower dynamics (see Supporting Information Figure S4), an expedient already adopted in other works . The higher mass of CG water molecules leads to simulation stability of up to 80 fs timestep, but results show a steady increase of dynamic viscosity with mass (see Supporting Information Figure S5) in agreement with literature values . The scaled density and RDFs, instead, are in excellent agreement with the reference values even with the largest timestep tested.…”

“… 45 The higher mass of CG water molecules leads to simulation stability of up to 80 fs timestep, but results show a steady increase of dynamic viscosity with mass (see Supporting Information Figure S5 ) in agreement with literature values. 46 The scaled density and RDFs, instead, are in excellent agreement with the reference values even with the largest timestep tested.…”

Effects of Water Deuteration on Thermodynamic and Structural Properties of Proteins and Biomembranes

“…While feasible for neat water, such simulations become prohibitively expensive when large biomolecules are added to the solution. However, as already demonstrated by Feynmann and Hibbs, zero point energy effects can effectively be incorporated into classical simulations by modifying the interaction potential. , We have recently employed this approach to develop, based on an earlier model, a classical force field for heavy water. Here, we use this approach to quantify the differences in thermodynamic and structural properties of amino acids, proteins, and phospholipid membranes in light vs heavy water, comparing the simulation result to experiment whenever possible and providing a molecular interpretation of the observed phenomena.…”

A Hydrophilic Mixed Lanthanide Metal–Organic Framework Monitoring H2O in D2O

“…The difference between D 2 O and H 2 O is mainly D and H, causing applications of D 2 O in nuclear reactions as a neutron moderator and in spectroscopic measurements as a solvent . Also, the boiling point of D 2 O (101.43 °C) is higher than that of H 2 O (100 °C), helping to produce D 2 O by distillation . However, strong hydrogen-bonding interactions exist between H 2 O and D 2 O, causing D 2 O to have strong hygroscopicity.…”

“…15 Also, the boiling point of D 2 O (101.43 °C) is higher than that of H 2 O (100 °C), helping to produce D 2 O by distillation. 16 However, strong hydrogen-bonding interactions exist between H 2 O and D 2 O, causing D 2 O to have strong hygroscopicity. So, it is valuable to monitor the H 2 O content in D 2 O.…”