Toward ab initio molecular dynamics modeling for sum-frequency generation spectra; an efficient algorithm based on...

Area of Science:

• Physical Chemistry
• Spectroscopy
• Computational Chemistry

Background:

• Sum-frequency generation (SFG) spectroscopy probes interfacial water O-H stretch modes.
• Computational methods using molecular dynamics (MD) link SFG spectra to water structures.
• Current MD methods require long trajectories (nanoseconds), limiting advanced simulations.

Purpose of the Study:

• To develop an efficient algorithm for calculating SFG spectra.
• To reduce the computational cost of SFG spectral analysis.
• To enable the use of advanced MD techniques for interfacial water studies.

Main Methods:

• Developed an efficient algorithm based on the surface-specific velocity-velocity correlation function (ssVVCF).
• Calculated SFG spectra using ssVVCF with short MD trajectories (∼100 ps).
• Validated the ssVVCF method against the dipole moment-polarizability time correlation function approach.

Main Results:

• The ssVVCF formalism significantly reduces computational costs by nearly an order of magnitude.
• SFG spectra calculated with ssVVCF accurately reproduce results from longer trajectory methods.
• Applied ssVVCF to ab initio MD simulations, showing no positive feature at 3100 cm⁻¹ in the imaginary component.

Conclusions:

• The ssVVCF algorithm provides a computationally efficient and accurate method for SFG spectral analysis.
• This advancement facilitates the study of interfacial water structures using advanced computational techniques.
• The findings offer new insights into the spectral signatures of interfacial water, particularly concerning the 3100 cm⁻¹ feature.