Investigating the Ground-State and Ionization Processes of Hydrogen Peroxide Dimers Using Sequentially Combined Theoretical Approaches

We present a study of the structures and ionization energies (IEs) of a series of conformations of hydrogen peroxide (H₂O₂) dimers. Ground-state properties were computed using the coupled-cluster with single, double, and perturbative triple excitations, CCSD(T), method with large correlation-consistent basis sets, while the ten lowest-lying IEs of the H₂O₂ dimer conformations were determined through the use of the equation-of-motion ionization potential coupled-cluster with single and double excitations method (EOMIP-CCSD) combined with correlation-consistent basis sets, extrapolation to the complete basis set limit, and consideration of core-correlation effects. All of the stable conformations were determined to be within 10 kJ/mol of the most stable structure (conformation I). The first IE of conformation I was determined to be 11.72 eV, while the corresponding value for conformation V was calculated as 11.58 eV. This difference (which was also noticed for other low-lying IEs and conformations) may be helpful for the assignments of experimental results. Given that the H₂O₂ clusters were first isolated through the use of beam experiments in the recent years, it is expected that the present work can call the attention of the community. In addition, the use of the combined theoretical approaches employed regarding the selection of the relevant conformations and the exploration of the corresponding ionization processes for the molecular clusters may present an initial guide for researchers venturing into the field.