Superalkali behavior of ammonium (NH4+) and hydronium (OH3+) cations: a computational analysis

Superalkalis are unusual species having ionization energy (IE) lower than that of alkali atom. The examples of typical superalkali cations include FLi2+, OLi3+, NLi4+, etc. Ammonium (NH4+) and hydronium (OH3+) cations form a variety of inorganic as well as organic compounds. Structurally, NH4 and OH3 appear a close analog of NLi4 and OLi3, respectively. However, there is no study on the superalkali nature of OH3 and NH4 to the best of our knowledge and belief. This work highlights whether NH4+ and OH3+ are superalkali cations, like NLi4+ and OLi3+ for the first time. Our ab initio calculations suggest that NH4 possesses lower IE than Li atom. However, the IE of OH3 is found to be comparable to that of Li. Furthermore, NH4 interacts with a superhalogen forming a supersalt and reduces CO2 into CO2−. These two characteristics of NH4 resemble to those of NLi4. These findings suffice to establish NH4+ as a superalkali cation. This may offer further opportunities to play with well-known NH4+ on a different ground.