Benchmark MRCI Study of Halogen Oxides: Potential Energy Surfaces and Spectroscopic Constants for X2, XO, and X2O (X = F, Cl, Br).

High-level quantum chemical methods (MRCI+Q and MRCI+P) combined with large correlation-consistent basis sets (aug-cc-pVnZ, where n = Q, 5, 6), were used to investigate the ground-state potential energy curves (PECs) and surfaces (PESs) of the X2, XO, and X2O systems (with X = F, Cl, Br). For the triatomic systems, the potential energy data obtained from MRCI+Q/aug-cc-pVQZ calculations in two different Jacobi representations were interpolated using the reproducing kernel Hilbert space (RKHS) method to construct smooth and accurate analytical representations of the PESs. This work provides a detailed comparison of the bonding characteristics of these molecules with those reported in previous studies. It lays the groundwork for future investigations of their dynamics and reactivity.