Molecular Dynamics-Instantaneous Frequencies of Molecules Method to Address the Performance of Classical and Rigid...

Area of Science:

• Computational Chemistry
• Molecular Dynamics Simulations
• Spectroscopy

Background:

• Accurate molecular force fields (FFs) are essential for reliable molecular dynamics (MD) simulations.
• Benchmarking FFs necessitates methods probing environmental fluctuations' impact on interaction potentials.

Purpose of the Study:

• To utilize the Molecular Dynamics-Instantaneous Frequencies of Molecules (MD-IFM) method for benchmarking molecular force fields.
• To evaluate vibrational spectroscopic descriptors (central frequencies, fluctuation amplitudes, spectral diffusion times) from MD simulations.
• To assess common water FFs against the MB-pol potential and analyze solvation structure and dynamics.

Main Methods:

• Application of the MD-IFM method to compute vibrational spectroscopic observables from MD simulations.
• Evaluation of several classical water FFs (TIP3P, SPC/E, TIP4P/Ew, TIP5P, OPC) against the MB-pol potential.
• Analysis of computed descriptors to probe solvation structure and dynamics.

Main Results:

• Classical FFs accurately predicted vibrational frequencies but underestimated local environment heterogeneity (σ).
• Classical FFs exhibited faster spectral diffusion dynamics (lower τc) compared to MB-pol.
• Shortcomings in classical FFs are attributed to simplified hydrogen-bonding network representations.

Conclusions:

• The MD-IFM method is validated as an efficient and robust tool for force field benchmarking.
• Classical water FFs show limitations in capturing the full complexity of water's local environment and dynamics.
• MD-IFM provides valuable insights into force field accuracy for solvation studies.