A surprisingly simple correlation between the classical and quantum structural networks in liquid water.

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Materials Science

Background:

• Nuclear quantum effects (NQE) are crucial for understanding liquid water's macroscopic properties, including structure, dynamics, spectroscopy, and transport.
• Classical simulations often fail to accurately represent these properties across a wide temperature range due to limitations in nuclear quantum effects.
• Accurate molecular interactions transferable across the phase diagram require proper accounting of NQE.

Purpose of the Study:

• To investigate the impact of nuclear quantum effects on the hydrogen-bonded structural networks in liquid water.
• To compare classical and quantum descriptions of nuclei using interaction potentials with differing NQE.

Main Methods:

• Simulations of liquid water using classical (class) and quantum (qm) nuclear descriptions.
• Employed two distinct interaction potentials: q-TIP4P/F (minimal NQE) and TTM3-F (significant NQE).
• Analyzed hydrogen-bonded structural networks and applied linear temperature scaling to compare results.

Main Results:

• Classical and quantum results for structural networks could be superimposed over a 250–350 K temperature range.
• A model-dependent linear temperature scaling law (T^(qm) = α T^(class) + ΔT) was identified.
• Specific scaling parameters were found for each potential: (α=0.99, ΔT=-6 K) for q-TIP4P/F and (α=1.24, ΔT=-64 K) for TTM3-F.

Conclusions:

• The structural networks from quantum and classical treatments are fundamentally similar across an extended temperature range.
• A linear temperature scaling law effectively reconciles classical and quantum simulations for these potentials.
• This suggests that molecular interactions can be transferable across temperatures when NQE are appropriately scaled.