Using phase-space Gaussians to compute the vibrational states of OCHCO

In this article, we use momentum-symmetrized phase-space Gaussians to calculate the vibrational energy eigenstates of the OCHCO⁺ cation. A potential energy surface provided by Bowman's group was used, albeit refit to a sixth order anharmonic force field. We have developed the "Crystal" algorithm to implement various basis set truncation strategies for our calculations. These calculations were performed using the SwitchBLADE code, designed by our group, which constructs and diagonalizes the vibrational Hamiltonian matrix in order to compute energy eigenstates. A theoretical overview of the Crystal algorithm is presented, as is a discussion of how best to truncate the basis for a floppy double-well system. Specific vibrational transition frequency results for OCHCO⁺ are also presented and analyzed.