Analytical harmonic vibrational frequencies with VV10-containing density functionals: Theory, efficient...

Area of Science:

• Computational chemistry
• Quantum chemistry
• Density Functional Theory (DFT)

Background:

• The VV10 nonlocal density functional is crucial for incorporating long-range correlation and dispersion effects in modern DFT functionals.
• Existing implementations provide energies and analytical gradients for VV10, but lack analytical second derivatives.

Purpose of the Study:

• To derive and implement the analytical second derivatives of the VV10 energy.
• To assess the performance of VV10-containing functionals for predicting harmonic vibrational frequencies.
• To provide recommendations for grid size and basis set convergence and present scaling factors for experimental comparisons.

Main Methods:

• Derivation and implementation of analytical second derivatives for the VV10 functional.
• Assessment of VV10-containing functionals (B97M-V, ωB97X-V, ωB97M-V) using the developed code.
• Studies on frequency convergence with respect to grid size and basis set.

Main Results:

• The computational cost of VV10 contributions to analytical frequencies is minimal for recommended settings.
• VV10's contribution to harmonic frequencies is small for small molecules but significant for systems with weak interactions.
• VV10-based functionals like B97M-V, ωB97M-V, and ωB97X-V perform well for water clusters.

Conclusions:

• The efficient implementation of VV10 analytical second derivatives facilitates accurate vibrational frequency calculations.
• VV10-based functionals are highly recommended for studying systems dominated by weak interactions.
• Recommendations for computational parameters and scaling factors are provided for improved accuracy.