The geometric structures, energetic and electronic properties of global minima of the AlBen (n = 1–12) clusters have been systemically studied by using the hybrid density functional theory [B3LYP] and coupled cluster [CCSD(T)] methods. It is found that the impurity Al atom is externally bound to the host Ben framework and its maximum coordination number is six. Besides, the geometries of AlBen bear close resemblance to either local or global minimum structures of Ben+1. The AlBe3 and AlBe8 clusters exhibit high relative stability among the AlBen clusters, which is reflected by the evolutions of average atomic binding energy, dissociation energy, second difference in energy, adsorption energy of Al, and HOMO-LUMO gap with cluster size. In comparison to the pure Ben+1 clusters, AlBen exhibit larger binding energy values, whereas they are more polarizable.
By doping two potassium atoms among three C20F20 cages, peanut-shaped single molecular solvated dielectron C20F20@K@C20F20@K@C20F20 as new type of spin molecular switches was theoretically presented. The triplet structure with two single-excess-electrons individually inside left and middle cages is thermodynamically more stable than the singlet one with lone pair of excess electrons inside middle cage. It is found that applying an oriented external electric field (OEEF) of 111 × 10-4 au (0.5705 V/Å) or -120 × 10-4 au (-0.6168 V/Å) in the x-axis direction firstly and then releasing it, the field-free triplet C20F20@K@C20F20@K@C20F20 with two single-excess-electrons can change into singlet one with lone pair of excess electrons through a singlet one with lone pair of excess electrons inside the end cage. Different spin states can bring significantly different dipole moment component values and considerable different intensities of maxumum wavelengths in intense absorption band. Therefore, C20F20@K@C20F20@K@C20F20 is a good candidate for spin molecular switching materials.
Based on the combination of novel carbon material graphynes (GYs) and superalkalis (OM3), a class of graphyne superalkali complexes, OM3+@(GY/GDY/GTY)– (M = Li, Na, and K), have been designed and investigated by density functional theory method. Computational results reveal that these complexes with high stability can be regarded as novel superalkali salts of graphynes due to electron transfer from OM3 to GYs. For second order nonlinear optical response, these superalkali salts exhibit large first hyperpolarizabilities (β0). Two important effects on β0 values are found, namely the atomic number of alkali atom in superalkali and the pore size of graphyne. Integrating the two effects, the selected combination of OLi3 with large pore size GTY can bring the considerable β0 value (6.5×105 au), which is a new record for superatom-doped graphynes. In the resulting complex, the OLi3 molecule is located at the center of the pore of GTY, forming a planar structure with the highest stability among these salts. Besides large β0 values, these superalkali salts of graphynes have deep-ultraviolet working region, hence can be considered as a new kind of high-performance deep-ultraviolet NLO molecules.
A intriguing type of excess electron compounds simultaneously containing electride and alkalide characteristics was obtained on the basis of the synthesized facially polarized molecule all-cis 1,2,3,4,5,6-hexafluorocyclohexane (1). By doping the two different faces of this Janus molecule with an alkaline earth atom and an alkali-metal atom, a series of M-1-M’ (M = Be, Mg, and Ca; M’ = Li, Na, and K) compounds were firstly achieved. Our calculated results show that, different from Be and Mg, one 4s electron of Ca can be transferred to the upper alkali metal atoms forming an alkali metal anion while the remaining 4s electron was push away from Ca+ yielding an electron anion by the instinctive facial polarization of 1 or with the assist of oriented external electric fields (OEEFs). Owing to the existence of two loosely bound excess electrons in the resulting Ca+-1-M’− (M’ = Li, Na, and K), these novel compounds exhibit extremely large first hyperpolarizabilities (β0) of 9.94 × 105‒1.81 × 106 au. Thus, we hope that this work could provide the first members with both of electride and alkalide characteristics to further enrich the family of excess electron compounds.