Diffuse-functions effects on theoretical calculation of disulfide dianion in water

Abstract Polysulfide anions play crucial roles in the liquid phase, but they are difficult to describe in theoretical calculations. We have investigated diffuse functions dependent total energy, bond length, and molecular orbitals for disulfide dianion (S22−) in water using conventional ab initio unrestricted Hartree-Fock method (UHF/6-311G+(d)) with a polarizable continuum model (PCM, e = 78.39) by changing ς value of diffuse functions. S22− in water turns out to be more stable than S2 and S2−, though it is too unstable to exist in vacuum so that the excess electrons will auto-detach. The optimal ς value that gives a local minimum of total energy for S22− in water is found to be 0.12. These new findings will contribute toward using more appropriate diffuse functions for other polysulfide anions as well.