Competition between alkalide characteristics and nonlinear optical properties in OLi3MLi3O (M = Li,Na, and K) complexes

Alkalides possess enhanced nonlinear optical (NLO) responses due to localization of excess electrons on alkali metals. Employing MP2/6‐311 + G(d) level, we design novel alkalides by placing alkali atoms (M) between two Li₃O superalkalis. We notice a competition between alkalide characteristics and NLO properties in OLi₃? M? Li₃O (M = Li, Na, and K) isomers. For instance, the atomic charge on M (q _M) in D _2h structure is ?0.58e for M = Li and its first static mean hyperpolarizablity (β _o) is 1 a.u., but in C _2v structure, q _M = ?0.12e and β _o= 3.4 × 10³ a.u. More interestingly, the β _o value for M = K (C _2v) increases to 1.9 × 10⁴ a.u. in which q _M = 0.24e . These findings may provide new insights into the design of alkalides, an unusual class of salts and consequently, lead to further researches in this direction.