Nitrate Superhalogens as Building Blocks of Hypersalts

High electron affinity triggered by lithium coordination: quasi-chalcogen properties of Li2Sn8Be

This work puts forward an unusual but rational strategy to design superatoms mimicking the properties of group VIA elements. A stable dianion with closo-configuration, namely Li2Sn8Be2−, has been obtained by...

Superhalogens Among 3d-Metal Compounds: MF4, MF6, MF12, and MF18 (M = Sc-Zn)

The ground states of the neutral and anionic tetrafluoride and hexafluoride series of 3d-metal atoms from Sc to Zn were assigned by using a double-check approach in which the pure and hybrid density functional methods were interchangeably used. It was confirmed that all these neutral fluorides are superhalogens except for TiF₄. The electron affinities of the hexafluorides were shown to be consistently higher than those of the tetrafluorides in accordance with the superhalogen conception of the extra electron delocalization over a larger number of the electronegative ligands. In the search for mononuclear fluorides possessing higher electron affinities, we considered the M(F₂)₆^- and M(F₃)₆^- series where M = Sc-Zn. We found that the optimized geometrical structures in both series may be described as MF₆^-- k(F₂), k = 3 and 6, of which the geometry of the MF₆^- core mimics that of the corresponding hexafluoride anion and the F₂ dimers are kept in a bound state by polarizing forces. In these cases, the electron affinity is decreased by tenths of eV with respect to the electron affinity of the core hexafluorides due to a confinement of the extra electron by the F₂ environment.

Greatly Enhanced Electron Affinities of Au2n Cl Clusters (n = 1-4): Effects of Chlorine Doping

Au2n Cl- (n = 1-4) clusters are investigated by both laser ablation mass spectrometry and theoretical calculations. It is interesting to find that the electron affinities of neutral Au2n Cl (n = 1-4) clusters are much larger than those of corresponding pure Au2n clusters. Among them, the electron affinity of Au2Cl is 4.02 eV, which can be defined as a very unique superhalogen that is quite different from classical ones of M n X m (M = metal, X = halogen, and n < m). Natural bond orbital and highest occupied molecular orbital analyses indicate that the extra electron is predominantly delocalized over the positively charged metal moiety in these anionic Au2n Cl- clusters, which is the main reason for the large electron affinities of the corresponding neutral species.

Exploring the structure, bonding and stability of noble gas compounds promoted by superhalogens. A case study on HNgMX3 (Ng = Ar-Rn, M = Be-Ca, X = F-Br) via combined high-level ab initio and DFT calculations

A series of complexes (HNgMX₃), formed from superhalogen MX₃ (M = Be-Ca, X = F-Br) noble gas (Ar-Rn) and the hydrogen atom, were investigated via combined high-level ab initio and DFT calculations. The high vertical electron detachment energy (VDE) of the superhalogen part will lead to charge transfer from the noble gas hydride to it. This charge transfer gives rise to attractive ionic interaction between the two components and to the existence of these complexes as local minima on the potential energy surface eventually. However, the VDE value of the superhalogen part is not always monotonically correlated with the thermodynamic/kinetic stability of the whole complexes. Therefore the superhalogen itself might not be enough to provide information for the correct prediction of the properties of the whole composites. Although there are exothermic channels of dissociation, the existence of energy barrier might ensure the existence of these Ng hydrides under certain conditions. Our analysis indicates the existence of two important factors, functioning in opposite directions, for the energy barriers along the exothermic channel. To achieve a high energy barrier, the attractive interaction between superhalogen and the H atom in the TS, which lowers the barrier, needs to be suppressed effectively. An understanding of the superhalogen-based composites will provide valuable information on the functional properties and potential application of superhalogens. The details of the interaction between different parts of these composites should be one of the areas of focus in these studies.

Oxidizing Metal Oxides with Polynuclear Superhalogen: An ab Initio Study

The ability of metal oxides (CoO, CuO, MgO, MnO₂, NiO, SiO_2, TiO₂, and ZnO) to form stable systems with polynuclear superhalogen (i.e., Mg₃F₇) is examined on the basis of theoretical considerations supported by ab initio calculations. It is demonstrated that the MeO _n ( n = 1, 2) molecules (such as CoO, CuO, MgO, MnO₂, NiO, TiO₂, ZnO) should form stable and strongly bound (MeO _n)⁺(superhalogen)^- salts when combined with the Mg₃F₇ superhalogen radical (acting as an oxidizing agent). This conclusion is supported by providing: (i) structural deformation of superhalogen upon ionization, (ii) predicted charge flow between each MeO _n and superhalogen (which allows estimating the amount of electron density withdrawn from MeO _n molecule during the ionization process), (iii) the localization of the spin density distribution, and (iv) the interaction energies and vertical ionization potentials (VIPs) for the compounds obtained at the CCSD(T)/6-311+G(d) level of theory. On the other hand, the Mg₃F₇ superhalogen was found to be incapable of ionizing molecules whose adiabatic ionization potentials (AIPs) exceed 12 eV (e.g., SiO₂). I believe that the results provided in this contribution may likely be of prospective relevance in the future studies on the issue of binding and preventing metal oxide nanoparticles aggregation in the environment before they occur harmful to human health and environment.

Why do higher VDEs of superhalogen not ensure improved stabilities of the noble gas hydrides promoted by them? A high-level ab initio case study

A series of 20 composite structures, consisting of superhalogen and noble gas (Ng) hydrides, was explored via high-level coupled-cluster single, double and perturbative triple excitations calculations in this work. The existence of these composites, as local minima on the potential energy surface, arises from the charge transfer from the Ng hydride part to the superhalogen moiety. Clearly, this transfer could lead to stabilizing the interaction of the ionic type between the two components. The driving force of the charge transfer should be the high vertical electron detachment energy (VDE) of the superhalogen part leading to its enough capability of extracting the electron from the Ng hydride moiety. However, except triggering the ionic attractive interaction, there is nomonotonic correlation between the VDE value and the thermodynamic stability of the whole composite. This counter-intuitive result actually originates from the fact that, irrespective of various superhalogens, only two of their F ligands interact with the Ng atoms directly. Thus, although leading to higher VDE values, the increase in the number of electronegative ligands of the superhalogen moiety does not affect the stabilizing interaction of the composites here directly. In other words, with the necessary charge transfer generated, further increase of the VDE does not ensure the improvement of the thermodynamic stabilities of the whole composite. Moreover, in the transition state of the exothermic dissociation channel, more F atoms will give rise to higher probability of additional attractions between the F and H atoms which should lower the energy barrier. That is to say, increasing VDE, i.e., having more F atoms in many cases, will probably reduce the kinetic stability. Knowing the inevitable existence of the exothermic channel, kinetic stability is crucial to the ultimate goal of experimental observation of these Ng hydrides. Thus, in some cases, only the superhalogen itself may not provide enough information for the correct prediction on the properties of the whole composites. The understanding of the superhalogen-based composites will provide valuable information on the functional properties as well as the application potential of superhalogen clusters. Thus, the corresponding researches should focus on not only the superhalogen itself but also other related aspects, especially the details of the interaction between different parts.

Computational investigation of LiF containing hypersalts

This study explores the design of possible hypersalts starting from the hyperhalogen Li₃F₄ plus a Li atom and the hyperalkali Li₄F₃ plus a F atom.

Iron-based magnetic superhalogens with pseudohalogens as ligands: An unbiased structure search

We have performed an unbiased structure search for a series of neutral and anionic FeL₄ (L = BO₂, CN, NO₂, NO₃, OH, CH₃, NH₂, BH₄ and Li₂H₃) clusters using the CALYPSO (Crystal structure Analysis by Particle Swarm Optimization) structure search method. To probe the superhalogen properties of neutral and anionic FeL₄ clusters, we used density-functional theory with the B3LYP functional to examine three factors, including distribution of extra electron, pattern of bonding and the nature of the ligands. Theoretical results show that Fe(BO₂)₄, Fe(NO₃)₄ and Fe(NO₂)₄ can be classified as magnetic superhalogen due to that their electron affinities even exceed those of the constituent ligands. The magnetic moment of Fe atom is almost entirly maintained when it is decorated with various ligands except for neutral and anionic (Li₂H₃)₄. Moreover, the current work is also extended to the salt moieties formed by hyperhalogen/superhalogen anion and Na⁺ ion. It is found that these salts against dissociation into Na + FeL₄ are thermodynamic stable except for Na[Fe(OH)₄]. These results provides a wealth of electronic structure information about FeL₄ magnetic superhalogens and offer insights into the synthesis mechanisms.

Super/hyperhalogen aromatic heterocyclic compounds

Aromatic heterocyclic molecules with negative electron affinity values can be transformed to highly oxidizing super/hyperhalogens based on a systematic in silico approach.

Probing the potential of halogen-free superhalogen anions as effective electrolytes of Li-ion batteries: a theoretical prospect from combined ab initio and DFT studies

The potential of superhalogens as efficient components of electrolytes in Li-ion batteries is verified from ab initio and DFT studies.

Theoretical characterization of a series of N5-based aromatic hyperhalogen 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.

Superhalogens: A Bridge between Complex Metal Hydrides and Li Ion Batteries

Complex metal hydrides and Li ion batteries play an integral role in the pursuit of clean and sustainable energy. The former stores hydrogen and can provide a clean energy solution for the transportation industry, while the latter can store energy harnessed from the sun and the wind. However, considerable materials challenges remain in both cases, and research for finding solutions has traditionally followed parallel paths. In this Perspective, I show that there is a common link between these two seemingly disparate fields that can be unveiled by studying the electronic structure of the anions in complex metal hydrides and in electrolytes of Li ion batteries; they are both superhalogens. I demonstrate that considerable progress made in our understanding of superhalogens in the past decade can provide solutions to some of the materials challenges in both of these areas.

Probing the structural and electronic properties of doped gallium oxide and sulfide, M(GaX2)2 where M = alkali or coinage metal; X = O, S

A theoretical study on the equilibrium geometries, vibrational frequencies and electronic features of a series of doped gallium oxide and sulfide clusters, M(GaX₂)₂ (M = alkali or coinage metal; X = O or S), was conducted.