title: Electronic and Vibrational Nonlinear Optical Properties of Five Representative Electrides.
abstract: The electrides have a very special electronic structure with diffuse excess electrons not localized on any specific atom. Such systems are known to have huge electronic nonlinear optical (NLO) properties. Here, we determine and analyze the vibrational, as compared to the electronic, NLO properties for a representative set of electrides: Li@Calix, Na@Calix, Li@B10H14, Li2(•+)TCNQ(•-), and Na2(•+)TCNQ(•-). The static and dynamic vibrational (hyper)polarizabilities are computed by the nuclear relaxation method (with field-induced coordinates and the infinite optical frequency approximation) at the UB3LYP level using a hybrid Pople basis set. In general, the static vibrational βvec and γ∥ exceed the corresponding static electronic property values by up to an order of magnitude. The same comparison for dynamic vibrational hyperpolarizabilities shows a smaller ratio. For the intensity-dependent refractive index (IDRI) and dc-Kerr processes, the ratio is on the order of unity or somewhat larger; it is less for the dc-Pockels and the electric field induced second harmonic (EFISH) effects (as well as the static α̅) but still important. The role of anharmonicity, motion of the alkali atoms, and substitution of Na for Li is discussed along with specific aspects of the charge distribution associated with the excess electron.
authors.affiliation: Institut de Química Computacional and Departament de Química, Universitat de Girona, Campus Montilivi, 17071 Girona, Catalonia, Spain.
authors.forename: Marc
authors.initials: M
authors.lastname: Garcia-Borràs
authors.affiliation: Institut de Química Computacional and Departament de Química, Universitat de Girona, Campus Montilivi, 17071 Girona, Catalonia, Spain.
authors.forename: Miquel
authors.initials: M
authors.lastname: Solà
authors.affiliation: Institut de Química Computacional and Departament de Química, Universitat de Girona, Campus Montilivi, 17071 Girona, Catalonia, Spain.
authors.forename: Josep M
authors.initials: JM
authors.lastname: Luis
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106, United States.
authors.forename: Bernard
authors.initials: B
authors.lastname: Kirtman