Search

FeCl4− and BF4− are very stable superhalogen anions, and FeCl4− possesses a magnetic moment of 5 μB due to the singly occupied 3d5 orbitals of the Fe3+. This letter determines the lowest energy structures and stabilities of anionic and neutral Fe(BF4)4−/0 and investigates the magnetic hyperhalogen property by using density function theories and configuration interaction method. The binding and dissociation energies indicate that both the anionic and neutral species are stable. The most stable structure of the anion has D2d symmetry in which the four BF4 units are coordinated to the central Fe atom in bidentate manner. The vertical and adiabatic detachment energies of Fe(BF4)4− reach 10.53 and 9.76 eV, respectively. The 3d orbitals of the central Fe atom form strong covalent bonds with the BF4 units, and the magnetic moments (5 μB) are formed by delocalized spin orbitals. Magnetic hyperhalogen Fe(BF4)4 is designed and the lowest energy structures of the anionic and neutral Fe(BF4)4-/0 are determined. The binding and dissociation energies show that both the anionic and neutral species have enhanced stabilities. The 3d orbitals of the central Fe atom form strong covalent bonds with the BF4 units and the anion has a magnetic moment of 5 μB. The most stable structure of the anion has D2d symmetry with vertical/adiabatic detachment energies 10.53/9.76 eV. The most stable structure of the neutral Fe(BF4)4 has Cs structure and the corresponding vertical/adiabatic detachment energies are 9.84/8.42 eV. [ABSTRACT FROM AUTHOR]

The geometries, stabilities and electronic structures of AlnCum (n = 5–9, m = 1–3) clusters were explored by using the genetic algorithm combined with ab initio methods. The geometric structures are almost spherical when the valence electrons are around the magic number 20, otherwise the structures are oblate or prolate. The stabilities of the clusters are related to both the Cu/Al ratios and the electronic configurations. The clusters with lower Cu/Al ratios have high stabilities. The molecular orbitals are in accord with the shell structures predicted by the jellium model. The 3d orbitals of the Cu atoms are localised, although their orbital energies are between the 1P and 1D jellium orbitals. The Al6Cu2 with 20 valence electrons forms closed 1S21P61D102S2 shells, and shows large binding energy and removal energy, large ionisation potential and small electron affinity. For the no-magic clusters, the structure deformation leads to crystal-field-like splitting of the degenerate shells and stabilises the clusters. [ABSTRACT FROM AUTHOR]

By using genetic algorithm combined with B3LYP and QCISD methods, this paper investigates the stabilities and electronic structures of Al6OMm (M = Na, K; m = 2,4,6) and a few other AlnXNam (X = C, N, O) clusters. The results show that the nonmetal doped metal clusters with 26 valence electrons have enhanced stabilities and large energy gaps. This paper extends the Jellium model for the application to the nonmetal doped metal clusters and explains the electronic origin of this strong magic structure. The nonmetal X atom is situated in the centre of the magic clusters. The 2s/2p orbitals of the central atom interact strongly with the superatomic 1S/1P orbitals and form bonding and antibonding orbitals. The bonding orbitals make the C/N/O atoms form s2p6 shell closure, and the antibonding orbitals make the metal moieties form closed 2S22P6 shells. The 26 valence electrons form closed s2p6S2P6D10 shells, and this electronic configuration can be taken as the combination of the octet rule and 18-electron rule. The octahedral Al6O2− core is a superatomic anion with great stability, and it can be used as building blocks to assemble Zintl phase materials by interaction with alkali metals. [ABSTRACT FROM AUTHOR]

Cluster-based materials are candidate materials for solid-state hydrogen storage owing to their special geometric and electronic structures. The surface adsorption and the encapsulated storage of H 2 molecules in a cagelike (MgO) 12 cluster have been studied using density functional theory (DFT) calculations including a dispersion interaction. The results revealed that the cagelike (MgO) 12 cluster surface can adsorb 24 H 2 molecules with an average adsorption energy of 0.116 eV/H 2 , which brings about a gravimetric density of 9.1 wt%. Compared with dispersion-corrected DFT calculations, the traditional DFT method substantially underestimates the surface adsorption strength. According to symmetric configurations, a maximum capacity of six H 2 molecules can be stored in the interior space of the cagelike (MgO) 12 cluster. The encapsulated H 2 molecules are trapped by stepwise energy barriers of 0.433–2.550 eV, although the storage is an endothermic process. The present study will be beneficial for hydrogen storage in cagelike clusters and assembled porous materials. [ABSTRACT FROM AUTHOR]

The low-energy structures of Al8Sim(m= 1–6) have been determined by using the genetic algorithm combined with density functional theory and the Second-order Moller-Plesset perturbation theory (MP2) models. The results show that the close-packed structures are preferable in energy for Al–Si clusters and in most cases there exist a few isomers with close energies. The valence molecular orbitals, the orbital level structures and the electron localisation function (ELF) consistently demonstrate that the electronic structures of Al–Si clusters can be described by the jellium model. Al8Si4corresponds to a magic number structure with pronounced stability and large energy gap; the 40 valence electrons form closed 1S21P61D102S21F142P6shells. The ELF attractors also suggest weak covalent Si–Si, Si–Al and Al–Al bonding, and doping Si in aluminium clusters promotes the covalent interaction between Al atoms. [ABSTRACT FROM AUTHOR]

Genetic algorithm combined with the semi-empirical Hamitonian AM1/PM3 is used to search the low energy isomers of AlSi (n = 3, 5, m ≤ 3 and n = 4, m ≤ 4) and the charged clusters with 20 and 28 valence electrons. The candidate structures were optimized by the density functional theory PBE0 and B3LYP models with the triply split basis sets including polarization functions. The electronic structures show that Al-Si binary clusters behave like metal clusters. The molecular orbitals accord with that predicted by the jellium model, and the electron localization function shows the valence electrons are delocalized over the entire clusters. The clusters having 20 and 28 valence electrons exhibit pronounced stabilities and large energy gaps. The 20 valence electrons of AlSi and AlSi , AlSi form closed shells 1 S 1 P 2 S 1 D . AlSi and AlSi have oblate structures and the P, D, F levels spilt considerably in these clusters. The electron density distributions suggest that doping silicon in the aluminum clusters enhances the stability considerably. [ABSTRACT FROM AUTHOR]

The low-energy structures of Al 5 Na m (m = 1–5) and Al 6 Na m (m = 0–4) are searched by using the genetic algorithm combined with MOPAC package. The stabilities and the electronic structures are studied by density functional theory models and by first principle perturbation theory at MP4 level. The results show that the Na atoms are located at the outside of the clusters. Analysis on the density of states and the charge distribution indicate the sodium atoms transfer their 3s electrons to aluminum and exist as +1 cations. The molecular orbitals agree with the types predicted by the jellium model, and Al 5 Na 5 and Al 6 Na 2 show enhanced stabilities as the 20 valence electrons form closed electronic shells. However, the valence orbitals don’t encompass the Na + cores. The electron localization function clearly demonstrates that the valence electrons reside at the outside of the Al 3+ cores, and the Na + cores are exposed at the outside of the valence electrons. All the results confirm that Al n moieties in the Al Na binary clusters form Zintl anions and the Na + cations are ionically bonded to them. It suggests Al Na clusters can be used as building blocks to form cluster-assembled Zintl-phase materials. [ABSTRACT FROM AUTHOR]

FeCl4− and BF4− are very stable superhalogen anions, and FeCl4− possesses a magnetic moment of 5 μB due to the singly occupied 3d5 orbitals of the Fe3+. This letter determines the lowest energy structures and stabilities of anionic and neutral Fe(BF4)4−/0 and investigates the magnetic hyperhalogen property by using density function theories and configuration interaction method. The binding and dissociation energies indicate that both the anionic and neutral species are stable. The most stable structure of the anion has D2d symmetry in which the four BF4 units are coordinated to the central Fe atom in bidentate manner. The vertical and adiabatic detachment energies of Fe(BF4)4− reach 10.53 and 9.76 eV, respectively. The 3d orbitals of the central Fe atom form strong covalent bonds with the BF4 units, and the magnetic moments (5 μB) are formed by delocalized spin orbitals. Magnetic hyperhalogen Fe(BF4)4 is designed and the lowest energy structures of the anionic and neutral Fe(BF4)4-/0 are determined. The binding and dissociation energies show that both the anionic and neutral species have enhanced stabilities. The 3d orbitals of the central Fe atom form strong covalent bonds with the BF4 units and the anion has a magnetic moment of 5 μB. The most stable structure of the anion has D2d symmetry with vertical/adiabatic detachment energies 10.53/9.76 eV. The most stable structure of the neutral Fe(BF4)4 has Cs structure and the corresponding vertical/adiabatic detachment energies are 9.84/8.42 eV. [ABSTRACT FROM AUTHOR]

AlnSi12−nN12 (n = 0, 1, 2, and 4) are electron redundant systems. The calculations show that the stabilities of AlnSi12−nN12 and Al12N12 are very close. One Si atom in each Si2N2 square protrudes obviously and the cages are distorted. The excess electrons reside at the outside of the protrudent Si atoms as lone pair electrons. They occupy antibonding orbitals and form the highest occupied band. The Si–N bonds are covalent bonds with strong polarity. The overlap integral is 0.38 per Si–N bond and is 17% stronger than the overlap in Al12N12. The atoms in molecule charge on the in-plane and protrudent Si atoms are 3.13e and 1.65e, respectively. The lone pair electrons form large local dipole moments enhance the electrostatic interaction between the protrudent Si and N atoms. The energy gaps of the electron redundant cages AlnSi12−nN12 (n = 0, 1, 2, and 4) are about 1 eV smaller than the gap of Al12N12. As the lone pair electrons are loosely bond, the SiN-based cages have large hyper-polarizabilities and so have potential applications, such as nonlinear optical materials. [ABSTRACT FROM PUBLISHER]

Abstract: The electronic structure of , and the related species HfF n and WF n is studied using ab initio methods. Computation reveals that the hafnium fluorides are much more stable than the corresponding tungsten fluorides. The detachment energy of is 8.8eV, whereas the corresponding quantity of is only 3.9eV. These results show that can be photodetached while is unaffected, and so it is possible by using photodetachment to suppress the interfering isobar 182W in the ion beam of 182Hf. Such information is the precondition for the successful implementation of a future photodetachment process in Accelerator Mass Spectrometry. [Copyright &y& Elsevier]

Molecular engineering plays a critical role in the development of electron donor and acceptor materials for improving power conversion efficiency (PCE) of organic photovoltaics (OPVs). The halogenated acceptor materials in OPVs have shown high PCE. Here, to investigate the halogenation mechanism and the effects on OPV performances, based on the density functional theory calculations with the optimally tuned screened range-separated hybrid functional and the consideration of solid polarization effects, we addressed the halogenation effects of acceptor ITIC, which were modeled by bis-substituted ITIC with halogen and coded as IT-2X (X = F, Cl, Br), and PBDB-T:ITIC, PBDB-T:IT-2X (X = F, Cl, Br) complexes on their geometries, electronic structures, excitations, electrostatic potentials, and the rate constants of charge transfer, exciton dissociation (ED), and charge recombination processes at the heterojunction interface. The results indicated that halogenation of ITIC slightly affects molecular geometric structures, energy levels, optical absorption spectra, exciton binding energies, and excitation properties. However, the halogenation of ITIC significantly enlarges the electrostatic potential difference between the electron acceptor and donor PBDB-T with the order from fluorination and chlorination to bromination. The halogenation also increases the transferred charges of CT states for the complexes. Meanwhile, the halogenation effects on CT energies and electron process rates depend on different haloid elements. No matter which kinds of haloid elements were introduced in the halogenation of acceptors, the ED is always efficient in these OPV devices. This work provides an understanding of the halogenation mechanism, and is also conducive to the designing of novel materials with the aid of the halogenation strategy. [ABSTRACT FROM AUTHOR]

Single-layer blue phosphorus (SLBP) has displayed charming photoelectric performances, but its property in hydrogen storage is not outstanding due to the weak interactions. To expand the application of SLBP in hydrogen storage, we attempt to screen SLBP-based materials with stable structures and strong polarity using density functional theory by doping lightweight elements and grafting alkali metal atoms. The simulation results indicate that the lightweight elements (B, C, N, O and F) doped SLBP systems have more stable structures due to the strong orbital interaction than pure SLBP, and exhibit electron deficient characteristics. Compared to the pure SLBP, the H 2 adsorption energies of the doped systems improve and range from 0.05 to 0.09 eV, but it still cannot meet the requirements of ideal hydrogen storage. Therefore, the lightweight element doped SLBP systems are further grafted by Li atom. Under the synergistic effect of doping lightweight elements and grafting Li atoms, H 2 molecules are strongly polarized, and the corresponding adsorption energies of H 2 reach to 0.16, 0.26, 0.28, 0.30, and 0.10 eV, respectively. It is worth emphasizing in the C-doped SLBP system that the hydrogen storage capacity of reaches 5.53 wt% for each Li atom adsorbs one hydrogen molecule and the corresponding adsorption energy is 0.23 eV/H 2 when the ratio of C to P atoms increases to 6:26. For each Li atom adsorbs two hydrogen molecules in the same hydrogen storage system, the hydrogen storage capacity reaches 10.48 wt% with 0.18 eV/H 2 adsorption energy. We hope these results can provide theoretical basis and scientific guidance for searching for SLBP-based materials with excellent hydrogen storage performances at ambient temperature. [ABSTRACT FROM AUTHOR]

• The C-doping enhances the stabilities of aluminum-alkali metal clusters. • Al 6 CM 4 (M = Li, Na, K) are magic clusters and Al 6 C4− forms a superatomic anion. • Al 6 CLi 4 is most stable as the alkali atoms are ionically bond to the central anion. • We extend the Jellium model to nonmetal doped metal clusters. The stabilities and electronic structures of Al 6 CM n (M = Li, Na, K; n = 2, 4, 6) are studied by evolutionary algorithm combined with ab initio methods. The strong attraction of the C4+ core to the valence electrons makes the 2S state considerably lower and the degenerated 2P6 being located in-between the split 1D10 states, so the 26 valence electrons form closed 1S21P62S21D102P6 shells. C-doping enhances considerably the stabilities of metal clusters. In Al 6 CM n clusters, the Al 6 Cq− with nearly all the valence electrons form Zintl anions and the M+ cations are ionically bonded on the peripheries. As Li+ has smallest radius, Al 6 CLi 4 possesses strongest thermal and chemical stabilities. The electronic structure of Al 6 C4− accords with the 8 + 18-electron rule and the Wade-Mingos rule, and can be regarded as a superatomic anion with specific stability. It can be used as building blocks to form Zintl phase structures by combining with metal counterparts. [ABSTRACT FROM AUTHOR]

Superatoms are clusters that mimic the chemistry of atoms and new materials with unique properties can be synthesized from them. Superalkali NM 4 clusters with homo- and hetero-alkalis M = Li, Na, K are designed, and their vertical ionization potentials (3.22 ∼ 3.74 eV) are lower than that of Cs atom. The stabilities of the superalkalis are guaranteed by the binding energies and positive energies of the dissociation channel NM 3 + M, and NLi 4 is the most stable among the NM 4 clusters. The high stability and tetrahedral geometry make these species idea units for building new materials. • Superalkali NM 4 clusters with homo- and hetero-alkalis M = Li, Na, K are designed. • The dissociation energies of the channel NM 3 + M confirm the thermal stabilities. • Their ionization potentials are lower than that of Cs atom. • NLi 4 is most stable with largest charge on Li atoms. [ABSTRACT FROM AUTHOR]

Abstract: An electron deficient fullerene B12C6N6 is studied by using ab initio calculations. The structure is generated by replacing N with C in the B12N12 cage to ensure only B–C and B–N bonds are formed. All the possible isomers are optimized and the low energy structures are determined. C and N atoms in the low energy isomers are inclined to segregate and form B2C2 and B2N2 squares. Natural bond analysis shows that the atomic orbitals of B, C and N in this cage hybrid approximately in sp2.3 and then form B–C and B–N bonds. The 2p orbitals perpendicular to the cage surface are partially occupied and the molecular orbitals formed by these orbitals are highly delocalized. The natural charge on N is about −1.17 in both B12N12 and B12C6N6, and the charge on C is −0.72 to −0.60. The molecular orbital compositions show that the B–N bonds are the same in B12N12 and B12C6N6, and the B–C bonds possess stronger covalent character. The HOMO of B12C6N6 is formed by 2p of B and C, and the LUMO is formed by 2p of C. The energy gap of C24, B12N12 and B12C6N6 is 2.52, 6.84 and 3.22eV, respectively. [Copyright &y& Elsevier]

The stabilities and electronic structures of Si m Al n-m N n and Si n N n (n = 16, 20, m = 12 and n = 24, m = 16) fullerene-like cages have been investigated using density functional method B3LYP and the second-order perturbation theory MP2. The results show that the Si m Al n-m N n and Si n N n fullerenes are more stable than the AlN counterparts. Comparing with the corresponding Al n N n cages, one silicon atom in each Si 2 N 2 square protrudes and the excess electrons reside as lone pair electrons at the outside of the protrudent Si atoms. Analyses on the electronic structures suggest that the Si N bonds are covalent bonding with strong polarity. The ELF (electron localization function) shows large electron pair probability between Si and N atoms. The orbital interactions between Si and N are stronger than that between Al and N atoms; the overlap integral is 0.40 per Si N bond in Si n N n and 0.34 per Al N bond in Al n N n . The AIM (atoms in molecule) charges on the Al atoms in Al n N n and Si m Al n-m N n are 2.37 and 2.40. The charges on the in-plane and protrudent Si atoms are about 2.88 and 1.50 respectively. Considering the large local dipole moments around the protrudent Si atoms, the electrostatic interactions are also favorable to the SiN cages. [ABSTRACT FROM AUTHOR]

Single layer blue phosphorus (SLBP) is a promising two–dimensional material for nanoelectronic devices, but the electronic structure and hydrogen storage property of modified SLBP received little attention. Li atoms can be strongly bonded on SLBP in a 1:1 Li/P ratio with a binding energy larger than the cohesive energy of bulk Li. The geometric structure of SLBP suggests the 3s3p orbitals of the P atom hybridize in sp 3 manner. But our analyses show that the 3s and 3p orbitals form bonding and antibonding orbitals respectively. The 3s orbitals are fully occupied as they have much lower energies, and the bonding orbitals formed by P 3p are occupied in pure SLBP. The decorated Li atoms transfer their 2s electrons to the antibonding orbital formed by P 3p. The Li atoms exist as +1 cations and they are ionically bonded on SLBP. H 2 molecules adsorbed on the Li + cations are strongly polarized and form strong adsorption. When two H 2 are adsorbed on each Li atom decorated at the 1:1 Li/P ratio, the hydrogen storage capacity reaches 9.52 wt% but the H 2 molecules are arranged in two layers with the adsorption energy −0.168 eV/H 2 . When the Li atoms are decorated alternatively on the two sides of the P 6 rings with a Li/P ratio of 1:2, each Li atom can absorb two H 2 molecules in a single–layer; the hydrogen storage capacity is 5.48 wt% and the adsorption energy reaches −0.227 eV/H 2 . These results mean the Li–decorated SLBP can work at ambient temperature with high reversible hydrogen storage capacity. [ABSTRACT FROM AUTHOR]

The adsorption of H 2 on B 24 N 24 , Al 24 N 24 and B 12 Al 12 N 24 clusters is studied by density functional theory calculations. Typical candidate isomers of B 24 N 24 , Al 24 N 24 and B 12 Al 12 N 24 are optimized and the lowest-energy structures are determined. H 2 adsorption on the three lowest-energy structures is investigated. The results show that H 2 is adsorbed on B/Al atoms in the side-on manner and on N atoms in the end-on manner. The adsorption of H 2 on Al sites is much stronger than the adsorption on B sites, and the mixing of B and Al as in B 12 Al 12 N 24 enhances the adsorption of H 2 obviously. After considering van der Waals interactions, the adsorption energies on Al, B and N are about −0.11 to −0.18, −0.05 and −0.04 to −0.06 eV, respectively. Interaction mechanisms between H 2 and the clusters are clarified by analyzing the electronic structures of the adsorption complexes. [ABSTRACT FROM AUTHOR]

• Al 6 CNa 4 is a magic cluster and Al 6 C4− forms a superatomic anion. • Cluster assembled structures from Al 6 CNa 4 are studied. • Electronic structures are preserved and the assembled crystal is a semiconductor. • The assembled structure shows high thermal and dynamic stabilities. Al 6 CNa 4 is a strong magic structure and Al 6 C4− forms a superatomic anion. Based on the geometric and electronic structures of Al 6 CNa 4 , a cluster assembled crystal is built. The electronic structures of the isolated cluster are well preserved and the assembled crystal is a superlight Zintl phase semiconductor. The interaction energy among the clusters reaches 3.12 eV per unit and the assembled structure shows high thermal and dynamic stabilities. Analyses on the bonding natures show that carbon doping contributes significantly to the stability of the cluster and the Al-C and Al-Al interactions are enhanced in the crystal. [ABSTRACT FROM AUTHOR]

The structures of Al 6 OK 2 and Al 7 N/CK are determined using unbiased genetic algorithm combined with ab initio methods. It was experimentally confirmed that Al 7 C− possesses exceptional stability. This study presets the interpretation for the hetero magic clusters. The delocalized Jellium orbitals of the metal moieties and the atomic orbitals of the nonmetal atom interact strongly and form bonding and antibonding orbitals. The orbital interactions lead to closed s2p6 shells of the nonmetal atom and the 18-electron S2P6D10 shells of the metal moieties. The 26 valence electrons correspond to a strong magic number. Al 6 OK 2 cluster is formed by ionically bonding two K+ cations to the Al 6 O2− anion. The electronic structures of Al 6 O2− core also accord with the Wade-Mingos rule. We build two typical ionic AB 2 crystals. The interactions between the building units reach 1.48 eV, and the phonon dispersion curves and elastic constants confirm the assembled structures are dynamically stable. [ABSTRACT FROM AUTHOR]