Performances of recently-proposed functionals for describing disulfide radical anions and similar systems

Two-center three-electron anions have been reported as a pitfall case for density functional theory, owing to their important dynamical correlation and the inherent difficulty of a balanced description of odd- vs. even-number electron bonds. The critical roles of the correlation functional, and of the amount of exact Hartree–Fock exchange included are investigated in order to pinpoint the most efficient approach for simulating disulfide radical anions (ease of formation and inter-sulfur distances). Several recently-developed functionals, such as B1B95, BMK, B2PLYP(D) and numerous range-separated hybrid yield a quantitatively correct description, and offer a pragmatic and superior solution to the Becke’s half-and-half usually recommended for this delicate situation.