Calculation of Vibrational Circular Dichroism Spectra Employing Nuclear Velocity Perturbation or Magnetic Field Perturbation Theory Using an Atomic-Orbital-Based Linear Response Approach

We present the implementation of an AO-based solver for vibrational circular dichroism (VCD) spectra calculations, employing nuclear velocity perturbation theory using velocity-gauge included in atomic orbitals or magnetic field perturbation theory using gauge-including atomic orbitals. The implementations are done within the Gaussian and plane waves framework in the CP2K package. The previously implemented approaches in CP2K are based on MO-solvers, which solve the Sternheimer equation for linear response. Our AO-solver implementations were validated against the MO-solver by performing VCD calculations for the R-enantiomer of mirtazapine. Additionally, we extended the AO-based solver implementation to nuclear displacement perturbation theory in order to calculate infrared absorption spectra. The AO-based solver produced spectra that matched exactly with the MO-based results, confirming the accuracy of the implementation. This allows for efficient calculations of vibrational properties, further extending the capabilities of CP2K for large molecular systems.