Structural properties and nonlinear optical responses of superatom compounds BF _4-M (M = Li, FLi _2, OLi _3, NLi _4)

摘要

A new type of superhalogen-(super)alkali compound, BF _4-M (M = Li, FLi _2, OLi _3, NLi _4), is theoretically characterized at the MP2/6-311+G(3df) level. The interaction between superhalogen BF _4 and different shaped (super)alkali M is found to be strong and ionic in nature. Bond energies of these BF _4-M species are in the range of 200.0-226.7 kcal/mol at the CCSD(T)/6-311+G(3df) level, which are much larger than the traditional ionic bond energy of 130.1 kcal/mol of FLi. In addition, different from the alkali halides, the BF _4-M compounds prefer to dissociate into ions rather than neutral fragments. The energetic properties of BF _4-M are found to be closely related to the size of the M subunit. The different effects of superalkali and superhalogen subunits on the nonlinear optical (NLO) properties of such superatom compounds are also revealed.