Modeling Harmonic and Anharmonic Local Low-spin Fe³⁺Molecular Magnet Qubit

The Fe³⁺ cationic molecular magnetic (MM) Qubit (Fe₃O(NC₅H₅)₃(O₂CC₆H₅)₆) is expected to exhibit stability in two distinct spin states. Currently, we have worked only with the low spin manifold, prompting us to calculate the infrared and Raman spectra. Moreover, we have performed the anharmonic corrections for this MM using Density Functional Theory (DFT) code NRLMOL implementation which calculates the Hamiltonian for each phonon space. An important factor is the zero-point vibrational energy (ZPVE) which is still present but is typically less than that predicted by a harmonic model. This is because anharmonicity leads to a decrease in the spacing between higher vibrational levels, thus affecting the overall energy distribution. The expectation is that vibrational effects would slightly stabilize the low-spin manifold.