Analytic polarizability and vibrational Raman spectra from constrained nuclear-electronic orbital density functional...

Area of Science:

• Computational Chemistry
• Spectroscopy
• Quantum Mechanics

Background:

• Simulating vibrational Raman spectra for systems with strong anharmonicity and nuclear quantum effects is computationally challenging.
• Accurate modeling is crucial for understanding molecular properties and dynamics.

Purpose of the Study:

• To apply and validate the constrained nuclear-electronic orbital (CNEO) framework for simulating vibrational Raman spectra.
• To assess the accuracy of CNEO-DFT and CNEO molecular dynamics (CNEO-MD) compared to conventional DFT.

Main Methods:

• Implementation of analytic static polarizabilities within the CNEO-DFT framework.
• Computation of Raman spectra using CNEO harmonic analysis and CNEO-MD.
• Extraction of spectral information from CNEO Hessian diagonalization and polarizability time-derivative autocorrelation functions.

Main Results:

• CNEO-DFT demonstrated substantially improved accuracy over conventional DFT for vibrational Raman spectra.
• The CNEO framework showed particular improvement for vibrational modes involving significant hydrogen motion.
• Successful application to formic acid and mixed water dimer/trimer systems.

Conclusions:

• The CNEO framework offers an accurate and efficient method for simulating vibrational Raman spectra.
• This approach is highly promising for systems where hydrogen motion is a critical factor.
• CNEO-DFT provides a powerful tool for computational spectroscopy.