A model study of hydrothermal reactions of trigonal dipyramidal Zn5 cluster with two water molecules

- An exhaustive search was performed for intermediate state in Zn and H2O reaction.
- Zn-H formation effectively reduces the energy.
- Zn-H is an intermediate in the reaction of Zn + H2O → ZnO + H2.
- H+ in Zn-H indicates a metal hydride character.

This paper explores the potentials of a systematic and exhaustive approach for searching intermediate states in the reactions between Zn and H2O. A system consisting of five Zn atoms (Zn5) forming a trigonal dipyramidal structure and fragments decomposed from two H2O to {H2O, OH−, O2− and H+}, were used. All the possible conformations consisting of Zn5 and fragments complex, 859 initial structures in total, were generated and optimized using quantum chemistry calculations. The optimized structure with the lowest energy was used as the initial structure for quantum MD simulation to generate the various conformations, and 600 snapshots including the initial structure were extracted and optimized using quantum chemistry. The sorting of energies revealed that Zn-H formation stabilized the Zn5 clusters and the water fragments. Thus, the intermediate states in the Zn and H2O reactions could be rationally detected. The current approach is not limited to special cases and can be used for a variety of reactions, in particular, for reactions between metal clusters and water molecules.