title: Nonlinear optical behavior of Li n F (n = 2-5) superalkali clusters.
abstract: Hyperlithiated clusters are known for their unusual bonding characteristics and lower ionization potentials. This study reports nonlinear optical (NLO) properties of a series of hyperlithiated clusters, Li n F (n = 2-5) for the first time. The structures of small Li n F (n = 2-5) clusters, obtained using second order Møller-Plesset perturbative method, are found to be stable against eliminations of F, F‾, and LiF. These Li n F species are stabilized by both ionic as well as covalent interactions. Our study shows that Li n F species can be thought of as superalkali-halogen (Li n  - F) clusters but belong to the class of superalkalies themselves. These clusters may also possess alkalide and/or electride characteristics due to excess electrons. The dipole moment, mean polarizability, and hyperpolarizability suggest their significant NLO responses which are explained using the highest occupied molecular orbital surfaces and TD-DFT analysis. The exceptionally large hyperpolarizability of Li2F (~10(5) a.u.) and its electride characteristics are particularly highlighted. This study may guide the researchers in the design of novel materials with significant NLO responses useful for electro-optical applications. Graphical Abstract Li2F superalkali resemble an electride in which the excess electron is pushed out by Li2 (+) moiety, leading to its high hyperpolarizability of order of 10(5) a.u.
authors.affiliation: Department of Physics, University of Lucknow, Lucknow, 226007, Uttar Pradesh, India.
authors.forename: Ambrish Kumar
authors.initials: AK
authors.lastname: Srivastava
authors.affiliation: Department of Physics, University of Lucknow, Lucknow, 226007, Uttar Pradesh, India. neerajmisra11@gmail.com.
authors.forename: Neeraj
authors.initials: N
authors.lastname: Misra
mesh_terms: D000468:Alkalies / Q000737:chemistry*; D004583:Electrons; D017611:Fluorine Compounds / Q000737:chemistry*; D007477:Ions; D018020:Lithium Compounds / Q000737:chemistry*; D008956:Models, Chemical; D055620:Optical Phenomena
chemical_list: D000468:Alkalies; D017611:Fluorine Compounds; D007477:Ions; D018020:Lithium Compounds
keywords: Ab initio calculations; Alkalide-electride; Hypervalent Lithium clusters; NLO properties; Superalkali