The creative concept of superatom brings a new dimension to the conventional periodic table, which has been gradually enriched by both theoretical and experimental research. In this article, we propose a new member, namely, Al12Be, to the superatom family. The amazing similarity between the Al12Be cluster and the chalcogen elements makes the former an excellent superatom counterpart of the latter. In addition, Al12Be exhibits more exothermic first electron affinity (EA) and less endothermic second EA values due to its size advantage over the chalcogen atoms, showing the superatom superiority in this respect. The stable compounds formed between Al12Be and other atoms, such as carbon, beryllium, calcium, and lithium, provide further evidence to support the quasi-chalcogen identity of Al12Be.

An electride molecule e–···K(1)+···calix[4]pyrrole···K(2)+···e– as an external electric field (F) manipulated nonlinear optical (NLO) switch is designed theoretically for the first time. As this molecule is an unusual singlet diradical electride molecule with two easily driven excess electrons (by electric field) at two opposite ends of the molecule, a novel switching mechanism of electronic structure isomerization emerges as a distinctive nonbonding evolution in the electride molecule. A small electric field driving leads to a long-range excess electron transfer from one side K(1) through the middle calix[4]pyrrole to the other side K(2), forms a lone excess electron pair of s-type rather than a single bond, and quenches the singlet diradical. Meanwhile, the molecular electronic structure becomes K(1)+···calix[4]pyrrole···K(2)+···2e–. Therefore, the small electric field driving brings a very high static first hyperpolarizability (β0) contrast from 0 (F = 0, Off form) to 4.060 × 105 au (F = a small nonzero value of 5 × 10–4 au, On form). Notably, under the electric field of 30 × 10–4 au, β0 reaches the largest value of 3.147 × 106 au and the molecule displays the most optimal NLO switching behavior. Furthermore, we consider also that 4H atoms of calix[4]pyrrole are substituted with 4F and 2Be atoms, respectively; then the 2Be and 4F substitution effects on the NLO switch in electride molecules are exhibited. This work opens a new research field of an electric field manipulated NLO switch of electride molecules.

Hyperhalogens are a class of highly electronegative molecules whose electron affinities even exceed those of their superhalogen ligands. Such species can serve as new oxidizing agents, biocatalysts, and building blocks of unusual salts, and hence are important to the chemical industry. Utilizing stable N5− as the ligand, a series of aromatic hyperhalogen anions, namely mononuclear M(N5)k+1− (M = Li, Be, B) and dinuclear M2(N5)2k+1− (M = Li, Be), have been reported here for the first time. Calculation results based on the density functional theory revealed that all the N5− subunits preserve their structural and electronic integrity as well as aromatic characteristics in these anions. Especially, these anionic molecules exhibit larger vertical electron detachment energies (6.76–7.86 eV) than that of the superhalogen ligand N5−, confirming their hyperhalogen nature. The stability of these studied anions is guaranteed by their large HOMO–LUMO gaps, and positive dissociation energies of predetermined fragmentation pathways. We hope this work will not only provide evidence of a new type of hyperhalogen molecule but also stimulate more research interest and efforts in the amazing superatom realm.

On the basis of stable alkaline earth metal ammines, a series of M(NH3)6NaCl and M(NH3)6Na2 (M = Mg and Ca) excess electron compounds were theoretically constructed and studied by using the density functional theory. The electride or alkalide characteristics of these compounds are verified by their electronic structures, HOMOs, and small VIE values. It is worth noting that the M(NH3)6Na2 alkalides have novel electronic structures that contain double alkali metal anions. As expected, all the noncentrosymmetric M(NH3)6NaCl and M(NH3)6Na2 compounds possess considerable first hyperpolarizabilities (β0) up to 123050 au, which can be attributed to low excitation energies (ΔEs) and large oscillator strength (f0) of their crucial excited states. In addition, results reveal that the Ca(NH3)6-based species with lower ΔEs and larger transition moments (Δμ) show larger β0 values compared with the corresponding Mg(NH3)6-based ones with similar geometries. This study may be significant in terms of designing excess electron compounds of new-type, especially alkalides with multiple alkali metal anions.

By doping the model complexant N3H3 with one or two lithium atoms, the geometrical and electronic structures as well as static electric properties of the resulting Li(N3H3), (N3H3)Li’ and Li(N3H3)Li’ complexes can be explored using the B3LYP, BHandHLYP, CAM-B3LYP and MP2 methods. All three complexes, especially Li(N3H3), were found to have large first hyperpolarizabilities (β0). Meanwhile, Li(N3H3) and Li(N3H3)Li’ exhibited electride and alkalide characteristics, respectively. The dependance of electric properties of alkalide Li(N3H3)Li’ on the alkali atoms involved and the complexant layer number were revealed by investigating the related M(N3H3)Li’ and Li(N3H3)M’ (M = Na and K), and Li(N3H3)nLi’ (n = 2, 3) systems. Note that the β0 value of alkalide M(N3H3)M’ increased not only with the increasing atomic number of the M’− anion but also with that of the M+ cation, which differs from previously reported cases. In addition, the electric properties of the Li(N3H3)Li’ alkalide were enhanced by increasing the complexant layers. However, it was found that both the complexant–complexant and the complexant–Li’ interactions reduced with the addition of N3H3 layers, so no stable structures were found for larger Li(N3H3)nLi’ complexes.

•The structures and properties of the CNLin0/+ (n = 1–10) clusters are studied.•The CN triple bond is completely cleaved in the CNLi100/+ clusters.•The CNLi8 and CNLi10 clusters show considerable low VIPs and large β0 values.The lowest-energy structures and stabilities of the heterodinuclear clusters, CNLin (n = 1–10) and relevant CNLin+ (n = 1–10) cations, are studied using the density functional theory with the 6-311 + G(3df) basis set. The CNLi6 and CNLi5+ clusters are the first three-dimensional ones in the CNLin0/+ series, respectively, and the CN group always caps the Lin0/+ moiety in the CNLin0/+ (n = 1–9) configurations. The CN triple bond is found to be completely cleaved in the CNLi100/+ clusters where the C and N atoms are bridged by two Li atoms. The CNLin (n = 2–10) clusters are hyperlithiated molecules with delocalized valence electrons and consequently possess low VIP values of 3.780–5.674 eV. Especially, the CNLi8 and CNLi10 molecules exhibit lower VIPs than that of Cs atom and can be regarded as heterobinuclear superalkali species. Furthermore, these two superalkali clusters show extraordinarily large first hyperpolarizabilities of 19,423 and 42,658 au, respectively. For the CNLin+ cationic species, the evolution of the energetic and electronic properties with the cluster size shows a special stability for CNLi2+.

A new kind of cationic superatom compounds (M–F)+ (M = OLi4, NLi5, CLi6, BLi7, and Al14) with low vertical electron affinities (VEA) has been designed based on the distinctive electronic structure of superalkaline-earth atom. The stability of the studied superatom architectures is guaranteed by strong M–fluorine interactions, considerable HOMO–LUMO gaps, as well as large dissociation energies. What is extraordinary is that fluorination plays an important role in lowering the VEA value of M+ and enables the resulting (M–F)+ fluorides to join the superalkali family. However, the same strategy does not work as well for the alkaline-earth atoms whose valence electrons are more tightly bound. The comparative study on (OLi4–X)+ (X = F, Cl, Br) reveals that fluorination is more effective than chlorination and bromination to reduce the VEA value of the OLi4+ cation. As for the (Al14–X)+ species, there is no obvious dependence of VEA values on halogen atomic number.

Superalkali Li3 dissolved in gaseous ammonia is investigated by density functional theory. Similar to the lithium atom, Li3 can coordinate up to four ammonia molecules. Among the structural isomers of Li3(NH3)n (n = 1–4), the one with separately distributed NH3 ligands is preferred. Most of the Li3(NH3)n species possess the alkalide characteristics and exhibit considerably large static first hyperpolarizabilities (β0) up to 3.9 × 105 au. Especially, for the lowest-energy Li3(NH3)n complexes, a prominent coordination number dependence of β0 is found as follows: 12608 (n = 1) < 38564 (n = 2) < 121726 (n = 3) < 391149 au (n = 4). In addition, the case of introducing a Na atom into such superalkali–ammonia systems has been considered and the resulting Li3(NH3)nNa (n = 1–4) complexes are studied in the same vein. It is revealed that the β0 values of Li3(NH3)nNa are influenced by both the coordination number and the relative position of NH3 ligands. We hope that this study could provide a new type of alkalides and raise the possibility of exploring a fresh, thriving area, i.e. superalkali solutions with solvents of all sorts.

A new series of polynuclear superalkali cations YLi4+ (Y = PO4, AsO4, VO4) has been characterized using ab initio methods. The central Y3− (PO43−, AsO43−, VO43−) acid radicals preserve their structural and electronic integrity in the first several lowest-lying isomers of YLi4+. Meanwhile, the introduction of Li+ cations can also dissociate an O2− ion from the Y3− groups. Besides, the AsO43− group is discerned to be separated into AsO2− and O22− fragments other than AsO3− and O2− units. This is why the AsO4Li4+ cation has been found to possess more diverse structures. The vertical electron affinities (EAvert) of the YLi4+ cations range from 2.44 to 4.67 eV, which are low enough to validate the superalkali or pseudoalkali identity of the title species. It is also noteworthy that the YLi4+ conformer with Td symmetry allows a more even distribution of the excess positive charge, and consequently exhibits the lowest EAvert value of ca. 2.45 eV.

•The global minimum structures of the oxygen-doped Ben (n = 1–12) clusters are identified.•Various energetic and electronic properties of BenO are compared with those of pure Ben+1 clusters.•The unique stability of Be11O qualifies itself for being considered as a magic number cluster.•Be11O achieves special stability from its two segments, namely Be112+ and O2− ions, respectively.The lowest-energy structures of the oxygen-doped Ben (n = 1–12) clusters are obtained at the B3PW91 level. Various energetic and electronic properties of the BenO clusters are systematically investigated using the QCISD(T) method, which are compared with those of pure Ben+1 clusters. The evolution of these properties with cluster size shows the unique stability of Be11O, which can actually be considered as an ionic compound (Be11)2+O2−. On the one hand, O2− has 8 valence electrons, satisfying the octet rule. On the other hand, the Be112+ moiety has a shell-closed electronic configuration, which renders itself particularly stable.

A new series of polynuclear superalkali cations YLi4+ (Y = PO4, AsO4, VO4) has been characterized using ab initio methods. The central Y3− (PO43−, AsO43−, VO43−) acid radicals preserve their structural and electronic integrity in the first several lowest-lying isomers of YLi4+. Meanwhile, the introduction of Li+ cations can also dissociate an O2− ion from the Y3− groups. Besides, the AsO43− group is discerned to be separated into AsO2− and O22− fragments other than AsO3− and O2− units. This is why the AsO4Li4+ cation has been found to possess more diverse structures. The vertical electron affinities (EAvert) of the YLi4+ cations range from 2.44 to 4.67 eV, which are low enough to validate the superalkali or pseudoalkali identity of the title species. It is also noteworthy that the YLi4+ conformer with Td symmetry allows a more even distribution of the excess positive charge, and consequently exhibits the lowest EAvert value of ca. 2.45 eV.

On the basis of stable alkaline earth metal ammines, a series of M(NH3)6NaCl and M(NH3)6Na2 (M = Mg and Ca) excess electron compounds were theoretically constructed and studied by using the density functional theory. The electride or alkalide characteristics of these compounds are verified by their electronic structures, HOMOs, and small VIE values. It is worth noting that the M(NH3)6Na2 alkalides have novel electronic structures that contain double alkali metal anions. As expected, all the noncentrosymmetric M(NH3)6NaCl and M(NH3)6Na2 compounds possess considerable first hyperpolarizabilities (β0) up to 123050 au, which can be attributed to low excitation energies (ΔEs) and large oscillator strength (f0) of their crucial excited states. In addition, results reveal that the Ca(NH3)6-based species with lower ΔEs and larger transition moments (Δμ) show larger β0 values compared with the corresponding Mg(NH3)6-based ones with similar geometries. This study may be significant in terms of designing excess electron compounds of new-type, especially alkalides with multiple alkali metal anions.

Hyperhalogens are a class of highly electronegative molecules whose electron affinities even exceed those of their superhalogen ligands. Such species can serve as new oxidizing agents, biocatalysts, and building blocks of unusual salts, and hence are important to the chemical industry. Utilizing stable N5− as the ligand, a series of aromatic hyperhalogen anions, namely mononuclear M(N5)k+1− (M = Li, Be, B) and dinuclear M2(N5)2k+1− (M = Li, Be), have been reported here for the first time. Calculation results based on the density functional theory revealed that all the N5− subunits preserve their structural and electronic integrity as well as aromatic characteristics in these anions. Especially, these anionic molecules exhibit larger vertical electron detachment energies (6.76–7.86 eV) than that of the superhalogen ligand N5−, confirming their hyperhalogen nature. The stability of these studied anions is guaranteed by their large HOMO–LUMO gaps, and positive dissociation energies of predetermined fragmentation pathways. We hope this work will not only provide evidence of a new type of hyperhalogen molecule but also stimulate more research interest and efforts in the amazing superatom realm.

Superalkali Li3 dissolved in gaseous ammonia is investigated by density functional theory. Similar to the lithium atom, Li3 can coordinate up to four ammonia molecules. Among the structural isomers of Li3(NH3)n (n = 1–4), the one with separately distributed NH3 ligands is preferred. Most of the Li3(NH3)n species possess the alkalide characteristics and exhibit considerably large static first hyperpolarizabilities (β0) up to 3.9 × 105 au. Especially, for the lowest-energy Li3(NH3)n complexes, a prominent coordination number dependence of β0 is found as follows: 12608 (n = 1) < 38564 (n = 2) < 121726 (n = 3) < 391149 au (n = 4). In addition, the case of introducing a Na atom into such superalkali–ammonia systems has been considered and the resulting Li3(NH3)nNa (n = 1–4) complexes are studied in the same vein. It is revealed that the β0 values of Li3(NH3)nNa are influenced by both the coordination number and the relative position of NH3 ligands. We hope that this study could provide a new type of alkalides and raise the possibility of exploring a fresh, thriving area, i.e. superalkali solutions with solvents of all sorts.