Vibrational second-order perturbation theory based on curvilinear coordinates: Thermochemical applications

Area of Science:

• Computational Chemistry
• Molecular Modeling
• Physical Chemistry

Background:

• Accurate calculation of molecular vibrational frequencies and thermodynamic functions is crucial for understanding chemical processes.
• Existing workflows face challenges with large, flexible molecules due to computational complexity.
• Anharmonic effects significantly influence molecular properties and require sophisticated theoretical treatment.

Purpose of the Study:

• To extend and improve a computational workflow for calculating anharmonic vibrational frequencies and thermodynamic functions.
• To enable the study of larger and more flexible molecular systems.
• To develop a more robust and accurate theoretical framework for molecular dynamics.

Main Methods:

• Extension of closed-form expressions for zero-point vibrational energies and partition functions.
• Application of second-order vibrational perturbation theory.
• Utilizing curvilinear internal coordinates to reduce couplings between degrees of freedom.
• Development of effective, low-dimensional, linear-scaling models.

Main Results:

• Demonstrated accuracy of the new implementation for prototypical systems.
• Successful application to complex molecular systems like molecular motors, nucleosides, and hormones.
• Validation of the approach for studying molecules with dozens of atoms.

Conclusions:

• The improved workflow provides a robust method for anharmonic vibrational frequency and thermodynamic function calculations.
• The use of curvilinear coordinates enhances the applicability to large and flexible molecules.
• This advancement facilitates systematic studies of complex molecular systems in computational chemistry.