DV-Xα Molecular Orbital Calculation Research Articles

Periodicity of Superatomic Hybrid Orbitals in Substituted Superatoms and Superatomic-like X@Ga12 (X = Li~Kr) Clusters

A superatom is a cluster composed of a specific number of atoms. We recently found that the superatom-like X@Ga12 (X = Li~Kr) clusters has the periodic energy levels of the specific orbitals 2S and 2P by means of the DV-Xα molecular orbital calculation method. This periodicity in energy levels has not been seen in 1D or 1F orbitals. We supposed that the periodicity of the energy levels of the 2S and 2P superatomic-like orbitals come from the same symmetry between atomic orbitals as the central atom X and the surrounding specific orbitals, according to the Jellium model. Both the s and p atomic orbitals of the central atom X in the superatom-like X@Ga12 have a large shielding effect, suggesting that the s and p atomic orbitals interact strongly with both 2S and 2P superatomic-like orbitals. The energy level periodicity has the potential to periodically change the number of electrons located in the 1D and 1F orbitals, which is related to magnetic properties and is expected to be useful for novel magnetic devices by periodically controlling the magnetism of superatoms.

Supramolecular Rare Sugar

We introduce rare sugars including their derivatives and supramolecular rare sugars, that have been actively researched at Kagawa University, Japan. Although the rare sugars are special sugars which hardly exist in nature, we has succeeded in mass synthesis of the rare sugars by utilizing biological enzyme isomerization reaction. In addition, the rare sugars have various functions such as blood sugar level suppressing function, cancer cell growth suppressing function, and antibacterial action. In addition, since rare sugars have a large number of hydroxyl groups, they have a possibility for using as devices for expressing various functions by employing them as ligands of transition metal complexes. In recent years, it is successful that we have synthesized the suplamolecular rare sugars (SRSs) from the different types of rare sugars, that is not as simple mixtures but as single crystals having supralattice structure, that can be freely controlled optical rotation. It has been found that the crystal structures of these SRSs mostly follow the Wallach rule, but do not satisfy the Wallach rule especially in the case of D, L-psicose. Therefore, we have investigated the single crystal X-ray structural analyses of SRSs, obtaining the detailed crystal structure data, and analyzed the intermolecular interaction between their sugar molecules in the crystal by means of the DV-Xα molecular orbital calculation. According to our detailed analysis of the research, calculating the intermolecular interaction revealed that the stability of the intermolecular interaction in the crystal can not be explained only by following the simple Wallach rule. Specifically, for example in the case of D, L-psicose, the total energy in a crystal can be stabilized by aligning the polarization vectors of the molecules, and as a result, we have clarified that the SRSs crystal structure can be stabilized, even if it does not follow the simple Wallach rule.

Considerarion of Superatomic Hibrid Orbital in superatom M@Al12 (M = Be, Mg, Ca, Sr)

We introduce a superatom, which is regarded as a modern alchemy and has been studied around the world. The superatom is a nanocluster composed of multiple atoms, for example Al13. Very interestingly, the “superatom” can mimic the chemical properties of “atom”, for example, the superatom Al13 exhibits the character of halogen atom, such as Cl. If this superatom is synthesized to an appropriate size freely, there is the possibility to be placed as an “artificial atom” in a three-dimensional periodic table, such as the conventional two-dimensional periodic table. In recent years, the exhaustion of rare metals has become a big problem, so that in the next generation of materials and devices, the superatom play as an important role, and it is expected to be used for various materials or as a substitute for expensive metal catalysts such as Pt. From these points of view, the superatom have been studied all over the world up to now, but there is not much studies on their electronic structures. Therefore, in this study, we have analyzed the electronic states of the chalcogen-encapsulated type superatom M@Al12 (M = Be, Mg, Ca, Sr) by means of DV-Xα molecular orbital calculation. Our research revealed that the electronic configuration of the superatom, which changed only the central atom, depends largely on the kind of doped atom. And we can also confirm the “superatomic hybrid orbitals (SAHOs)” composed of superatomic orbitals (SAOs), and chalcogen characteristics.

Mechanochemical Preparation of 8-Hydroxyquinoline/Hydroxyapatite Hybrid Nanocrystals and Their Photofunctional Interfaces

Hybrid nanocrystals of 8-hydroxyquinoline (8Hq) molecules and hydroxyapatite nanocrystals (HAp) were successfully prepared by a mechanochemical solid-state reaction. The hybrid nanocrystals exhibit a significant thermal stability and efficient photoluminescence peak at 500 nm, which were attributed to metal–ligand charge transfer at the interface between the oxygen atoms of 8Hq and the calcium ions of HAp, and the interfacial photofunctions were mechanochemically controlled. The interfacial bonding structures were also supported by a DV-Xα molecular orbital calculation.

Molecular orbital study on a mechanism of adhesion between carbides and optical glass with high refractive index

AbstractA mechanism of adhesion between carbide molds and optical glass species with high refractive index in precision molding was elucidated on the basis of DV‐Xα molecular orbital calculations. An interfacial cluster model comprising NbPNaO glass and glassy carbon (GC) was applied in order to examine the changes in the chemical bonds between atoms at the interface and the effect of the substitution of niobium with other transition metals (denoted with; MdI) at the interface. The bond overlap population (BOP) between oxygen atoms at the surface of the glass and carbon atoms at the surface of the GC increases when the surface of the glass approaches the GC, while that between MeIO correspondingly decreases. When introducing oxygen deficiency at the surface of the glass, the BOP of the MeIcarbon bonds against the MeIoxygen increased in the order of Nb<Ti<W, which mostly coincided with the experimentally obtained order of increased probability of occurrence of adhesion between the glass and the GC mold. This supports the validity of the model where adhesion between the glass and the carbide occurs following the reduction of the transition metal in the glass. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009

Highly-charged ion induced surface nano-modification

Nano-modification of highly-oriented pyrolytic graphite (HOPG) surfaces using slow highly-charged ion (HCI) beam irradiation has been demonstrated. Single HCI impact creates nanoscale protrusions in which the electronic structure is different from that formed by singly-charged ion impact. By combining slow HCI irradiation with electron injection onto the impact region, a transition of sp 2 to sp 3 hybridization is obtained, resulting in I– V characteristics of the impact region showing non-conductive properties with ∼ 6 eV band gap. The size of the features created by Ar 8+-impact on HOPG are about ∼ 1 nm in diameter at 400 eV kinetic energy, which corresponds with a region where electron emission occurs by the Coulomb potential of the HCI. Assuming that 20 carbon atoms are contained in the structure formed, we discuss plausible sp 3 carbon structures by means of Raman spectroscopic measurements and DV-Xα molecular orbital calculations. The energy level structure of the non-spherically symmetric sp 3 structure of 20 carbon atoms shows values of energy gap corresponding to those obtained in the experiment. The results presented suggest that single impact of HCI on solid surfaces creates new nanostructure features, and HCI would be a good tool for collective material-modification-processing with nanoscale controllability.

Electronic Structures of Dyes and Phthalocyanines Estimated with “Photo-Electron Spectroscopy in Air (PESA)”

AbstractThe near-edge electronic structures of several dyes and phtalocyanines were investigated using Photo-Electron Spectroscopy in Air (PESA). The ionization potentials (IPs) of N3, N719, Z907, D102, D149 and D205 were derived from observed photoemission threshold energies to be 5.88, 5.47, 5.44, 5.53, 5.44 and 5.49eV, respectively. Density of states (DOS) of Fe-, Ni-, Cu- and H2-phthalocyanines were deduced from differentiation of observed photoemission yields with incident photon energies. DOS thus obtained were well compared with calculated ones estimated with use of the DV-Xα molecular orbital calculation method.

パラジウム<110>対称傾角粒界の原子構造と電子状態

In this study, the energy and atomic structure of the symmetric tilt boundaries in palladium were calculated using a molecular dynamics (MD) method and the electronic structures of hydrogen in the bulk and at the grain boundaries were calculated using discrete-variational Xα (DV-Xα) molecular orbital cluster calculaion by solving Hartree-Fock-Slater equation. The result of MD simulation revealed that the energy of the symmetric tilt boundary of palladium depended on the misorientation angle and that there were large energy cusps at the misorientation angles which correspond to the {111}Σ3 and {113}Σ11 symmetric tilt boundaries. The atomic structure of all symmetric tilt boundaries could consist of the combination of the {331} Σ19, {111}Σ3 and {113}Σ11 structural units and {110}Σ1 and {001}Σ1 single crystal units. The result of DV-Xα molecular orbital cluster calculation showed that the interstitial hydrogen atoms induced the palladium-hydrogen chemical bond which had a different energy level from the palladium-palladium bond. The component of the palladium-hydrogen bond at the grain boundaries was similar to those in the bulk palladium. It is clarified that electronic structure near the grain boundary is different from that in the perfect crystal.

The electronic structures of crystalline and aqueous solutions of NaBr and NaBrO3 using in-situ Na K and Br L edge x-ray absorption spectroscopy

The electronic structures of crystalline and aqueous solutions of NaBr and NaBrO3 were studied using in-situ Na K and Br L edge x-ray absorption spectra measured under ambient conditions. Analyses of Na K-edge x-ray absorption spectra show that NaBr and NaBrO3 strongly dissociate in aqueous solution and form Na+ hydration structures, [Na(H2O)n]+ (n = 0–6). However, the size of the anions significantly affects the formation of the Na+ hydration structures in aqueous solutions. The ligand field potential (10 Dq) observed in the Br L-edge x-ray absorption spectra allows in determining their dependence not only on the coordination structure between the Br and the first near neighbor but also the second near neighbor in crystalline state, and, the hydration structure and the counter cations in aqueous solutions. DV-Xα molecular-orbital calculations predict that the transitions in the Br L-edge NEXAFS occur from Br 2p to the unoccupied states containing mainly 4d orbitals of Br for both crystalline and aqueous solution. However, 5s and 5p of Br and 3p of Na in addition to the 4d orbitals of neighbor Br for crystalline NaBr and 5s and 5p of Br, 2p of O and 1s of H for aqueous NaBr also contribute to the unoccupied states.

Structural Characterization of Chemical Species in Solution by a Theoretical Analysis of XANES Spectra

A theoretical analysis method using a discrete variational Xα (DV-Xα) molecular orbital (MO) calculation, based on electron transition from an inner orbital to an unoccupied orbital, is introduced to analyze X-ray absorption near-edge structure (XANES) spectra in a lower energy region below the X-ray absorption edge. The computational procedure is described in detail and the evaluation of an obtained result is also explained. Applications of this method are presented for Cu(II) ions in liquid ammonia, macrocyclic Cu(II) complex in aqueous solution, and Al(III) ions in aqueous solution.

Study of the O K α X-ray emission spectrum of the SiO 2–CaO binary slag by DV-Xα molecular orbital calculation

O K α X-ray emission spectra of SiO 2–CaO binary slags simulated by the DV-Xα molecular orbital calculation were compared with ones measured by EPMA. The composition of the slag has been incorporated in the calculation of the O 2p partial density of states (PDOS). The calculated O 2p PDOS as a function of the CaO content agreed well with the measured O K α X-ray emission spectra of the glassy state 62.4 mol% SiO 2–37.6 mol% CaO and 43.3 mol% SiO 2–56.7 mol% CaO binary slags. The present method was found to provide a useful means of clarifying the change in ionic configuration of the slag with metal oxide content, and also of understanding the concept of basicity.

Soft X-ray emission and absorption spectra in the O K region of oxygen incorporated in microporous carbon

Soft X-ray emission and absorption spectra in the O K region of oxygen incorporated in microporous carbon were measured using synchrotron radiation, in order to directly observe the oxygen and identify its chemical bonding states on the graphitic surface in microporous carbon. The O K X-ray emission spectrum exhibits a peak at 526 eV with a low-energy tail, and the absorption spectrum at the O K threshold exhibits a sharp peak at 531.5 eV and then rises from 535 eV. Spectral feature analysis using DV-Xα molecular orbital calculations show that the measured X-ray spectra are not sufficiently explained by H 2O or typical substituents, such as –OH, –CHO, and –COOH, on the graphitic surfaces.

Soft X-ray emission and absorption spectra in the C K region of sputtered amorphous carbon films

Soft X-ray emission and absorption spectra in the C K region of amorphous carbon films systematically deposited by RF, ion-beam, and ECR sputtering under various deposition conditions were measured using highly brilliant synchrotron radiation. A broad main peak and a high-energy shoulder were observed in the emission spectra, and a fine structure consisting of at least five peaks was observed in the absorption spectra. By analogy to the occupied/unoccupied C2p-DOS obtained by DV-Xα molecular orbital calculations of simple cluster models composed of sp 2 and sp 3 carbon atoms, we approximately explained the spectral features in the measured X-ray emission spectra by σ and π bonds and estimated the fine structures in the absorption spectra by the hybridized unoccupied molecular orbitals formed by the local-structures composed of sp 2 and sp 3 carbon atoms.

Syntheses and electronic structures of macrocyclic metal complexes with fullerene

New cocrystallines are reported that contain C 60 with anti-formed macrocyclic metal complexes of octaethylporphyrin (OEP). From the results of the electronic structure obtained using a DV-Xα molecular orbital calculation, the configuration of the OEP in a cocrystalline of C 60 with Ag(II)(OEP) or Ni(II)(OEP) is predicted to be the anti-formed structure. It is shown that the anti-formed configuration of the OEPs can be confirmed in Ag(II)(OEP)·C 60·2C 6H 6 and 2Ni(II)(OEP)·C 60·2C 6H 5Cl according to a structural prediction we have made by means of electronic structure calculations using the DV-Xα method. It is also revealed that the C 60 is located at the closest approach to the centered atom involving the 5:6 carbon ring junction in these cocrystallines. Using the DV-Xα method, it is predicted that new types of π–d material can be produced. The material should have high conductivity and a significant magnetic moment via the π–d interaction in the charge transfer salt of [Cr(III)(Por)] +[C 60] −.

XANES spectra of sesqui-oxides of Al, Cr and Fe

Abstract Oxygen X-ray absorption near edge (XANES) spectra obtained from α-Al 2 O 3 , Cr 2 O 3 and α-Fe 2 O 3 were found to be clearly distinguishable. The energy distributions of the XANES spectra were reproduced here fairly well by the DV-Xα molecular orbital calculation. On the other hand, O Kα spectra emitted from these oxides showed no significant difference. This indicates that the XANES is a very promising candidate to study the chemical environment of anions in typical ionic compounds.

Configurations of Benzene and Pyridine Molecules Adsorbed on Graphitic Surface of Microporous Carbon

The possible configurations of benzene and pyridine molecules adsorbed in microporous carbon were analyzed by synchrotron-radiation-excited soft X-ray emission spectroscopy and by analyzing its spectral features using DV-Xα molecular orbital calculations. The distances between the adsorbed molecules and the graphitic surface were estimated to be approximately 0.33 nm in both benzene- and pyridine-adsorbed systems. Both molecular orientations were also estimated to be almost parallel to the graphitic surface of microporous carbon. The electronic states of benzene and pyridine molecules adsorbed on the graphitic surface were similar to those of individual nonadsorbed free molecules. Therefore, the adsorption of benzene and pyridine molecules in the microporous carbon can be confirmed to be physisorption, and there is little charge-transfer between the adsorbed molecules and the graphitic surface.

Photoelectrochemical properties of TiO 2 rutile microalloyed with 4d and 5d transition elements

The microalloying effects of 4d and 5d transition metals on the photoelectrochemical properties of rutile titanium oxide are investigated by a series of experiments and DV-Xα molecular orbital calculation. Rutile TiO 2 and (Ti, M)O 2 oxides (M: Nb, Mo, Ta, W) can be made by the oxidation of pure Ti and Ti–5 mol% M alloys, respectively. The saturated photocurrent density of rutile (Ti, M)O 2 is dependent on the additional element, M, and it lowers in the order, Nb>Ta>Mo>W. The visible light response at 620 nm in rutile (Ti, Ta)O 2 and at 620 and 730 nm in rutile (Ti,W)O 2 is found by measuring the spectral dependence of anodic photocurrent density at 1000 mV vs. SCE. The experimental results can be explained by the calculated level structures of the microalloyed rutile oxides.

Structure and Electronic Properties of Amorphous Ge–Pd Alloys Manifesting the Metal-Insulator Transition. II. Photoemission Spectroscopy and Electronic Structure Calculations

Photoemission valence band spectra of amorphous Ge–Pd alloys produced by Ar-ion-beam sputtering are measured with XPS and UPS techniques over a wide range of Pd concentration. A Pd-derived band composed of Pd4 d -Ge4 p bonding states develops with Pd concentration and governs the upper valence band region in high concentrations. The UPS profile at the Fermi edge shows that a metallic continuous band is formed in alloys above 1.3% Pd. To interpret the photoemission spectra and reveal the electronic structure of these amorphous alloys, DV-Xα molecular orbital calculations are performed for Ge 17- n Pd n ( n =0, 1, 2, 4, 5) clusters with diamond structure which may simulate some local structures of amorphous alloys of low Pd concentrations. Calculated partial and total density of states well reproduce the valence band features revealed by XPS and UPS. A bandstructure change from an open band to a continuous band at the Fermi level caused by alloying with Pd is also confirmed by the calculation. The localizat...

X-ray emission and absorption spectra of carbon nitride films prepared by laser ablation

X-ray emission and absorption spectra of carbon nitride films prepared by laser ablation were measured. The carbon x-ray spectra of films obtained in a nitrogen atmosphere were different from those of a film prepared in vacuum. It was found from DV-Xα molecular orbital calculations on x-ray spectra that the films obtained in a nitrogen atmosphere contained bonding between carbon and nitrogen atoms. This was supported by the Fourier transform IR spectra. Copyright © 1999 John Wiley & Sons, Ltd.

Calculation of B K-V x-ray emission spectra of boron nitrides

The DV-Xα molecular orbital (MO) calculation method was applied to the B K–V x-ray emission spectra of hexagonal (h-), cubic (c-) and wurtzite (w-) type boron nitrides (BN). The calculated B 2p density of states (DOS) was in good agreement with the B K–V x-ray emission. The main peaks and low-energy satellite peaks in the B K–V x-ray emission spectra are due to the B 2p and the B 2p hybridized with N 2s, respectively. The high-energy satellite peak in the B K–V x-ray emission spectra clearly corresponds to the π* sub-band of the B 2p DOS in h-BN. However, the high-energy satellite peak observed in w-BN is not in agreement with the B 2p DOS. It is considered that the high-energy satellite peaks are due to less than four-coordinated B atoms such as have dangling bonds and defects in w-BN. In the B K–V x-ray emission spectra of h-BN, the synthesizing π and σ sub-bands of B 2p DOS could explain the polarized emission spectra very well. Copyright © 1999 John Wiley & Sons, Ltd.