The H2S dimer revisited - Insights from wave-function and density functional theory methods. Ab initio molecular dynamics simulations of liquid H2S

We performed an investigation of the hydrogen bonding in H2S dimers in gas-phase using HF, MP2, PBE, PBE0 and BLYP. A series of symmetry operations such as translations and proper and improper rotations were performed to the donor and acceptor molecules, and the energetic dependency of the H-bond as a function of these transformations was obtained. We found that the DFT methods predict a repulsive region around 5 to 6 times more repulsive that that obtained with the wave-function methods. Additionally, we determined the Lennard-Jones potential for the translations and derived a Morse potential for the different rotations and ab initio MD simulations were performed for liquid H2S. We found that remarkably, the length of the H-bonds and height of rotational barriers in liquid H2S are similar to the ones of the dimer. This is because of the weak and highly directional H-bonds in both the liquid and H2S dimer.