Vibrational Coupled Cluster Computations in Polyspherical Coordinates with the Exact Analytical Kinetic Energy...

Area of Science:

• Quantum chemistry
• Theoretical chemistry
• Molecular spectroscopy

Background:

• Traditional vibrational analyses often employ rectilinear coordinates.
• Rectilinear coordinates can struggle with complex molecular motions, hindering accurate anharmonic state calculations.
• Vibrational coupled cluster (VCC) theory is a powerful tool for computing molecular vibrational states.

Purpose of the Study:

• To investigate the efficacy of curvilinear polyspherical coordinates in VCC theory.
• To compare the performance of polyspherical coordinates against rectilinear coordinates (normal and hybrid) for molecular vibrational calculations.
• To assess the impact of coordinate choice on potential energy surface construction and vibrational state computations.

Main Methods:

• Implementation of polyspherical coordinates within an adaptive density-guided potential energy surface construction.
• Application of polyspherical coordinates in vibrational coupled cluster (VCC) calculations for anharmonic vibrational states.
• Comparison with full vibrational configuration interaction (VCI) calculations using rectilinear coordinates for formaldehyde.
• Calculations on hydrogen peroxide using the polyspherical coordinate parametrization.

Main Results:

• Polyspherical coordinates accelerate convergence in truncated VCC methods compared to normal coordinates.
• The polyspherical coordinate approach demonstrates robust performance, even for truncated methods.
• Effective treatment of complex internal molecular motions is facilitated by polyspherical coordinates, overcoming limitations of rectilinear approaches.

Conclusions:

• Curvilinear polyspherical coordinates offer a significant advantage for VCC calculations of anharmonic vibrational states.
• This coordinate system enhances computational efficiency and accuracy, particularly for molecules with intricate vibrational dynamics.
• The findings pave the way for more precise theoretical predictions in molecular spectroscopy and dynamics.