An accurate full-dimensional potential energy surface of the hydrogen sulfide dimer system and its kinetics for the hydrogen exchange channel

The hydrogen sulfide cluster exhibits weak interaction, which plays a crucial role in biomolecules, superconductivity, etc. Hydrogen sulfide dimer, (H2S)2, as a relatively simple system containing this interaction, is a preferred subject for studying this weak interaction and has attracted significant attention recently. In this work, an accurate full-dimensional potential energy surface (PES) for the (H2S)2 system is reported using the permutationally invariant polynomial-neural network (PIP-NN) method. The energies for the sampled 106,952 configurations are calculated using the CCSD(T)-F12a/AVTZ method, with the Boys-Bernardi counterpoise method used to eliminate basis set superposition errors (BSSE). The total root-mean square error (RMSE) of the final PIP-NN PES is only 0.019 kcal mol-1. The PES can reproduce well the structures, energies, and harmonic frequencies of the nine stationary points, five stationary isomers and four transition states. Two new hydrogen exchange reaction channels are included in the current PES. The rate coefficients of the hydrogen exchange channels are calculated using both conventional transition state theory (TST) and canonical variational theory (CVT) with the quantum tunneling correction treated by the zero-curvature tunneling (ZCT) and small curvature tunneling (SCT) methods.