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

Abstract

Superalkalis are unusual species having ionization energy (IE) lower than that of alkali atom. The examples of typical superalkali cations include FLi 2 + , OLi 3 + , NLi 4 + , etc. Ammonium (NH 4 + ) and hydronium (OH 3 + ) cations form a variety of inorganic as well as organic compounds. Structurally, NH 4 and OH 3 appear a close analog of NLi 4 and OLi 3 , respectively. However, there is no study on the superalkali nature of OH 3 and NH 4 to the best of our knowledge and belief. This work highlights whether NH 4 + and OH 3 + are superalkali cations, like NLi 4 + and OLi 3 + for the first time. Our ab initio calculations suggest that NH 4 possesses lower IE than Li atom. However, the IE of OH 3 is found to be comparable to that of Li. Furthermore, NH 4 interacts with a superhalogen forming a supersalt and reduces CO 2 into CO 2 −. These two characteristics of NH 4 resemble to those of NLi 4 . These findings suffice to establish NH 4 + as a superalkali cation. This may offer further opportunities to play with well-known NH 4 + on a different ground.