Electron correlation in benzene: A QMC study of neutral and charged states.

This article focuses on the application of variational Monte Carlo (VMC) and fixed-node diffusion Monte Carlo (FN-DMC) methods to investigate electron correlation effects in neutral and cationic benzene molecules. The study demonstrates that all-electron FN-DMC calculations yield correlation energies significantly lower than those obtained with the frozen-core approximation and traditional quantum chemistry methods like CCSD(T), highlighting the important contribution of core-electron correlations. FN-DMC also provides ionization potentials (both vertical and adiabatic) that closely match experimental values after zero-point vibrational energy corrections, outperforming Hartree–Fock (HF) estimates by incorporating substantial electron correlation effects. The results underscore FN-DMC's effectiveness in accurately capturing electron correlation in aromatic systems and emphasize the necessity of all-electron treatments for comprehensive electronic structure descriptions.