The dipole force components in nano-sized metal hydrides are quantitatively determined with curvature and x-ray diffraction measurements. Ab-initio density functional theory is used to calculate the dipole components and the symmetry of the strain field. The hydrogen occupancy in a 100 nm thick V film is shown to be tetrahedral with a slight asymmetry at low concentration and a transition to octahedral occupancy is shown to take place at around 0.07 [H/V] at 360 K. When the thickness of the V layer is reduced to 3 nm and biaxially strained, in a Fe0.5V0.5/V superlattice, the hydrogen unequivocally occupies octahedral z-like sites, even at and below concentrations of 0.02 [H/V].

The structures and nonlinear optical properties of a novel class of alkali metals doped electrides B 12 N 12 -M (M 5 Li, Na, K) were investigated by ab initio quantum chemistry method. The doping of alkali atoms was found to narrow the energy gap values of B 12 N 12 in the range 3.96-6.70 eV. Furthermore, these alkali metals doped compounds with diffuse excess electron exhibited significantly large first hyperpolarizabilities (b 0 ) as follows: 5571-9157 au for B 12 N 12 -Li, 1537-18,889 au for B 12 N 12 -Na, and 2803-11,396 au for B 12 N 12 -K. Clearly, doping of the alkali atoms could dramatically increase the b 0 value of B 12 N 12 (b 0 5 0). Furthermore, their transition energies (DE) were also calculated. The results showed that these compounds had low DE values in the range 1.407-2.363 eV, which was attributed to large b 0 values of alkali metals doped B 12 N 12 nanocage.

On the basis of stable all‐cis 1,2,3,4,5,6‐hexafluorocyclohexane, a series of alkali metal atom doped MF6C6H6 (M = Li, Na, and K) compounds were theoretically constructed and studied by using ab initio quantum chemistry method. The calculated results show that the HOMO–LUMO gap of the MF6C6H6 conspicuously narrowed from 10.41 eV of pure F6C6H6 to about 2.00 eV of MF6C6H6. The electride characteristics of MF6C6H6 are verified by their electronic structures, HOMOs, and small VIE values. As expected, these electrides possess considerable static first hyperpolarizabilities (β0). Among the studied electrides, the largest β0 of the LiF6C6H6 is 7.00 × 105 au, which is about 3030 times larger than pure F6C6H6. TD‐M06‐2X calculations show that these larger β0 values are attributed to lower transition energies for the crucial excited states of MF6C6H6 systems. Further, the vibrational contributions to the static first hyperpolarizabilities of these molecules are also estimated. Moreover, Li atom doped dimer and trimer of F6C6H6 also present unusual electride's features and exhibit dramatically large β0. Thus, the F6C6H6 interacting with the alkali metal atoms may be a potential promising NLO nanomaterial.

The geometrical structures, electrical properties, and nonlinear optical (NLO) properties of AlNNT-Li and BNNT-Li nanotube systems were investigated by means of the density functional theory (DFT) method. Frontier molecular orbitals and density of states analyses show that adsorption of the Li atom can significantly narrow the wide HOMO-LUMO gaps of pure AlNNT and BNNT. The results reveal that AlNNT-Li and BNNT-Li systems containing diffuse excess electrons can be regarded as inorganic electrides. The formation of diffuse excess electrons leads to a decrease in transition energies, thereby increasing the first hyperpolarizabilities (β ) of AlNNT-Li and BNNT-Li. This work may contribute to the development of potential high-performance NLO materials. Graphical abstract The structural characteristics and nonlinear optical properties of the AlNNT-Li and BNNT-Li systems were studied by means of density functional theory. Introduction of Li atoms greatly enhances the static first hyperpolarizabilities of AlNNT-Li and BNNT-Li.

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