Nitrate superhalogens as building blocks of hypersalts.

Using density functional theory (DFT) with a generalized gradient approximation for the exchange and correlation potential, we have studied the geometrical structure and electronic properties of NOx (x = 1-3), Li(NO3)x (x = 1,2), Mg(NO3)x (x = 1-3), and Al(NO3)x (x = 1-4) clusters. To validate the accuracy of the DFT-based method, calculations were also performed on small clusters using coupled cluster method with singles and doubles and noniterative inclusion of triples (CCSD(T)). With an electron affinity of 4.03 eV, NO3 behaves as a superhalogen molecule and forms the building block of hyperhalogens when interacting with metal atoms such as Li, Mg, and Al. This is confirmed by calculating the adiabatic detachment energies (ADEs) of Li(NO3)2, Mg(NO3)3, and Al(NO3)4, which are 5.69, 6.64, and 6.42 eV, respectively. We also demonstrate that these hyperhalogens can form salts when counter balanced by a cation such as K.