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Abstract Based on the density functional theory calculations, the BP-(B 3 N 3) n and Li@BP-(B 3 N 3) n (BP = biphenylene, n = 1–4) systems, were designed for the first time and explored the effects of Li doping and B 3 N 3 substitution on their nonlinear optical (NLO) properties. We find that, when the carbon rings are replaced by B 3 N 3 units in the biphenylene, systems of enhanced static hyperpolarizabilities (β 0) are delivered. And the position and the number of B 3 N 3 unit have an important effect on the β 0 value. Moreover, when one Li atom is adsorbed on the surface of B 3 N 3 -substituted BP, the β 0 values of these systems are further dramatically enhanced to 2.24 × 104–1.42 × 106 au. The further investigations show that small transition energy is the decisive factor for their large β 0 values. Specially, these Li-doped compounds exhibits high stability and excellent infrared (IR) transparency. These findings might provide valuable insights into the design of novel high-performance NLO materials based on BP flake. Highlights • The position and the number of B 3 N 3 unit have large influence on β 0 of BP-(B 3 N 3) n. • Li atom can further enhance the NLO response of the B 3 N 3 -substituted biphenylene. • The β 0 values of Li@BP-(B 3 N 3) n are much larger than those of Li@BP systems. • Absorption spectra shows that Li-doped molecules can be used as IR NLO materials. [ABSTRACT FROM AUTHOR]

A systematic analysis of electronic and nonlinear optical properties of a novel class of (super)alkali-doped complexes M/M 3 O@ g -C 3 N 4 (M Li, Na, K) is presented. These compounds exhibit considerable stability with large interaction energies, and M 3 O @g -C 3 N 4 has higher stability than the corresponding M @g -C 3 N 4. It is found that doping the (super)alkali can significantly narrow the wide energy gap of the pure g -C 3 N 4 in the range of 2.04–2.84 eV, and these doped g -C 3 N 4 show enhanced visible-light absorption. Due to the large charge transfer from (super)alkali to g -C 3 N 4 moiety, these doped compounds exhibited significantly large first hyperpolarizabilities up to 2165–63761 au. The ratio between the vibrational and electronic contribution on hyperpolarizability indicates that the vibrational contributions play an important role in determining the static hyperpolarizabilities of certain systems. Therefore, (super)alkali-doped g -C 3 N 4 are expected to be potential candidates for visible-light catalysis and high-performance nonlinear optical materials. We expect this work could provide a new idea for designing functional materials using superalkali clusters. [ABSTRACT FROM AUTHOR]

Abstract: 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. [ABSTRACT FROM AUTHOR]

On the basis of Hexamethylenetetramine (HMT), a new class of (super)alkali-doped electrides HMT−X, HMT−FX 2 , and HMT−OX 3 (X = Li, Na, and K) were designed in theory. The results reveal that superalkali FX 2 and OX 3 can keep their structural integrity in these studied compounds. These electrides possess significantly large first hyperpolarizabilities ( β 0 ) in the range of 0.65 × 10 3 –4.72 × 10 5 au due to diffuse excess electrons from chemical doping. It is found that the superalkali effect on the β 0 value is more significant than that of simple alkali doping. Furthermore, employing the heavier superalkali (FK 2 and OK 3 ) can dramatically enhance the β 0 values of the HMT−FK 2 and HMT−OK 3 . The further investigations show that small transition energies is the decisive factor for the large β 0 values of (super)alkali-doped electrides. The ratios between the vibrational and electronic contributions on (hyper)polarizability demonstrate that the vibrational contributions play an important role in determining the static (hyper)polarizabilities. This paper not only designs novel electrides with large NLO response but also expands the application range of superalkali cluster. [ABSTRACT FROM AUTHOR]