Structural and electronic properties of borazine cyclacenes

The structural and electronic properties of borazine cyclacenes (BNn) have been investigated by performing semiempirical molecular orbital self-consistent field calculations at the level of AM1 method within the RHF formulation. It has been found that as the number of borazine rings increases in the arenoid belt the structures become more exothermic.     

Structural and electronic properties of nanostructured HAlO

The results of a theoretical study of the nanostructured ternary compound HAlO are presented. We have considered isolated (HAlO)n clusters, the interactions between two such clusters, and two-dimensional layers of HAlO. In many of the calculations we used a parametrized density-functional tight-binding method in the calculation of the electronic properties for a given structure, combined with two different unbiased approaches, i.e., an "Aufbau" and a genetic-algorithm method, for optimizing the structure for clusters with n up to 26. The results for the isolated clusters are analyzed by means of similarity, stability, and shape parameters. Isolated structures with n up to 6 were also studied intensively with pure DFT methods.     

Structural and electronic properties of endohedral metallofullerenes

This account presents an overview of our achievements in structural and chemical understanding of endohedral metallofullerenes (EMFs), a new class of metal‐carbon hybrid materials formed by encapsulation of metals inside fullerene cavities. Structural determination of EMFs is of fundamental importance for understanding their intrinsic properties and the formation mechanism, and for broadening their applications. We have developed an effective method for determining the structures of paramagnetic EMFs, and also succeeded in observing the motion of cluster in a di‐metal EMF for the first time. Recently, we unambiguously established the structures of some carbide EMFs which had been wrongly assumed as conventional EMFs previously. More importantly, we have obtained some insoluble EMF species which had never been explored or even expected before. Meanwhile, the chemical properties of various EMFs with different cage structures or different metallic cores have been systematically investigated by means of both covalent and supramolecular considerations, yielding many fascinating results relating to the dictating effect of internal metals. It is noteworthy that all these achievements are based on unambiguous X‐ray results of pristine or functionalized EMFs. DOI 10.1002/tcr.201100038     

Structural and electronic properties of PFOS and LiPFOS

The structural and electronic properties of perfluorinated surfactants perfluorooctane sulfonate (PFOS) and lithium perfluorooctane sulfonate (LiPFOS) have been investigated theoretically by performing semi-empirical molecular orbital theory at the level of AM1 calculations. The optimized structure and the electronic properties of the molecules are obtained.     

Structural and electronic properties of some tetralene compounds

The PMR spectra of tetralene-2, 3-episulphide(I), -epoxide(II) and epiimine(III) have been measured and compared with those of the related compounds cis-tetralenediol-2, 3(IV) [1] and its acetal derivative(V). The electronic and structural properties of these compounds displayed some interesting trends. The data revealed the different deshielding effects of the heteroatoms.     

Structural and electronic properties of transition metal thiophosphates

From the viewpoint of metal coordination we examine the structural characteristics of several new members of transition metal thiophosphates (i.e., MPS phases with M = V, Nb, Ta), in which various ligands such as S²⁻, S²⁻₂, and phosphorus-sulfur polyanions P_nS^x−_m (1 ≤ n ≤ 4; 3 ≤ m ≤ 13; 2 ≤ x ≤ 6) provide either an octahedral or a bicapped prismatic coordination of the metal. Tight-binding band electronic structure calculations show that the low-lying acceptor orbitals responsible for lithium intercalation of thiophosphates are their d-block bands. This prediction is confirmed by our electrochemical lithium intercalation study which reveals that the reduction sites of thiophosphates are their metal cations. Molecular orbital calculations are carried out on vanadium compounds with extremely short interligand S···S contacts. The occurrence of such short contact distances is not caused by covalent bonding in the S···S contacts but by the small size of vanadium cations which forces its surrounding sulfur ligands to squeeze one another.     

Structural and electronic properties of a Benzoin monomer

In the present work, we report structural and electronic properties of a benzoin monomer named as 2-oxo-1,2-diphenylethyl-2-bromopropanoate (C₁₇H₁₄BrO₃). The previously synthesized compound is characterized by single crystal X-ray diffraction. The optimized molecular geometry (bond lengths, and bond angles), HOMO-LUMO analysis and molecular electrostatic potential (MEP) are calculated by density functional theory (DFT) and Hartree-Fock (HF) methods with 6-311G(d) basis set in the neutral ground state and using DFT methods for singly oxidized doublet, singly reduced doublet, and neutral triplet state for the benzoin compound. The X-ray structure determination of the compound is compatible with the geometric parameters calculated at B3LYP/6-311G(d). In the triplet state the HOMO-LUMO energy gap of 2.39?eV which indicates semi-conductor property is recommended for the photovoltaic devices.     

Structural and electronic properties of graphene nanotube-nanoribbon hybrids

The structural and electronic properties of a hybrid of an armchair graphene nanotube and a zigzag graphene nanoribbon are investigated by first-principles spin-polarized calculations. These properties strongly depend either on the nanotube location or on the spin orientation. The interlayer spacing, the transverse distance from the center of the ribbon and the stacking configuration affect the electronic structures. The antiferromagnetic configuration has a lower total energy than the ferromagnetic one. The interlayer atomic interactions between the two subsystems would change the low energy dispersions, open subband spacings, and induce more band-edge states. Moreover, such interactions create an energy gap and break the spin degeneracy in the antiferromagnetic configuration. The band-edge-state energies are sensitive to the nanotube location.     

Structural and electronic properties of compound metal clusters

The equilibrium geometries, relative stabilities, and vertical ionization potentials of compound clusters involving Li _n , Na, Mg, and Al atoms have been calculated using ab initio self-consistent field linear combination of atomic orbitals — molecular orbital (SCF-LCAO-MO) method. The exchange energies are calculated exactly using the unrestricted Hartree-Fock (UHF) method whereas the correlation correction is included within the framework of configuration interaction involving pair excitations of valence electrons. While the later correction has no significant effect on the equilibrium geometries of clusters, it is essential for the understanding of relative stabilities. Clusters with even numbers of electrons are found to be more stable than those with odd numbers of electrons regardless of their charge state and atomic composition. The equilibrium geometries of homo-nuclear clusters can be significantly altered by replacing one of its constituent atoms with a hetero-nuclear atom. The role of electronic structure on the geometries and stabilities of compound clusters is discussed.     

Structural and electronic properties of hydrated MgO nanotube clusters

Hydrated MgO nanotube clusters are constructed and studied by the density functional theory at the B3LYP/6-31G(d) level. A strong exothermicity chemisorption reactivity of MgO nanotube clusters with water, which releases 137.5–171.8 kJ/mol. The averaged charge of Mg ions is steady, and presents a stronger ionic bonding. Mg ions are more sensitive to the coordination number. For the reaction of water onto clusters, electronic properties of hydrated clusters have remarkable change compared with anhydrous clusters.     

Structural and electronic properties of small platinum metallorganic complexes

A theoretical first-principles study of Pt _n (ligand) _m (n = 1–3) metallorganic complexes is performed, by varying the number of metal atoms and the nature and number of organic coordinate ligands (specifically, vinylic and arylic ligands). For each system, the nature of the bonding, the structure and the energetics of the metal/organic-species interaction are analyzed to derive information on the growth of coated metal clusters in solution. It is found that two régimes can be distinguished: a “coordinatively saturated” régime, in which the ratio among the number of ligands and the number of metal atoms is high and a ligand/organic π-interaction mode is preferred, and a “coordinatively unsaturated” régime, in which the ligand/metal ratio is low and a ligand/organic σ-interaction mode is preferred. Reactive channels, such as oxidative insertion of Pt into C–H bonds with the corresponding formation of platinum hydride species, can be opened in the latter régime.     

Structural and electronic properties of fluorinated boron nitride nanotubes

The effects of F doping on the structural and electronic properties of the (5, 5) single-walled boron nitride nanotube (BNNT) are investigated by using the density functional theory method. The chemiadsorption of F maintains the hexagonal BN network, increases the lattice constant, and introduces acceptor impurity states. On the other hand, substitutional doping of F destroys the hexagonal BN network, decreases the lattice constant, but does not alter the insulating feature of the BNNT. The observed insulator-to-semiconducting transition, a lattice contraction, and a highly disordered atom arrangement in the sidewall of BNNTs upon F doping appear to be most reasonably attributed to a codoping of dominating substitutional F over chemiabsorbed F, which can induce deep donor impurity states, a lattice contraction, and a destruction of the hexagonal BN network simultaneously.     

Structural and electronic properties of Co-corrole, Co-corrin, and Co-porphyrin

A quantitative study of the structure and electronic properties of Co-corrole, Co-corrin, and Co-porphyrin, using density functional theory, is reported. The structure of each macrocycle is optimized, with no symmetry constraints, by considering different spin states. The ground-state structures and spin states (S = 1 for Co-corrole, S = 0 for Co-corrin and S = 1/2 for Co-porphyrin) are in good agreement with the experimental data available. The trends in the sizes of the coordination cavities upon varying the inner metal atom and/or the macrocycle are analyzed and compared with those for the Fe-porphyrin we studied previously. Our results reveal that most of the distortion of the Co-corrin core in the B12 coenzyme is due to the inherent properties of Co-corrin. Quite different behaviors are found between corrinoids and porphyrins upon varying the spin state. While an increase in the metal-nitrogen (M-N) distance with spin state occurs in the porphyrins, the corrinoids show little variation in the M-N distance and, in some cases, undergo small structural changes in the ring structure. These results aid in understanding the often discussed question of why nature has chosen corrin/porphyrin for carrying out the particular biological functions identified in the B12 coenzyme.     

Structural and electronic properties of sulfur passivated InP(100)

InP(100) surfaces were passivated with S using a wet chemical treatment. The structural properties of the passivated surface were studied with low-energy electron diffraction. In agreement with previous studies, a 1 × 1 pattern was observed for the as-passivated surface, while a 2 × 1 reconstruction was found for surfaces annealed at temperatures in the range 350 °C – 500 °C. Photoemission and inverse photoemission were used to examine the electronic properties of the surface. The sulfur treatment was found to remove both occupied and unoccupied states from the vicinity of the fundamental gap. The surface bandgap at the zone centre, Γ, on the passivated surface was measured to be 5.1 eV, as compared to 2.5 eV for the clean, sputter/annealed 2 × 4 surface. No partially filled bands were observed crossing the Fermi level.     

Structural, energetic, and electronic properties of hydrogenated titanium clusters

Hydrogen undergoes dissociative chemisorption on small titanium clusters. How the electronic structure of the cluster changes as a function of the number of adsorbed hydrogen atoms is an important issue in nanocatalysis and hydrogen storage. In this paper, a detailed theoretical investigation of the structural, energetic, and electronic properties of the icosahedral Ti13 cluster is presented as a function of the number of adsorbed hydrogen atoms. The results show that hydrogen loaded Ti13H20 and Ti13H30 clusters are exceptionally stable and are characterized by hydrogen multicenter bonds. In Ti13H20, the dissociated hydrogen atoms are bound to each of the 20 triangular faces of Ti13, while in Ti13H30, they are bound to the 30 Ti-Ti edges of Ti13. Consequently, the chemisorption and desorption energies of the Ti13H20 (1.93 eV, 3.10 eV) are higher than that of Ti13H30 (1.13 eV, 1.95 eV). While increased hydrogen adsorption leads to an elongation of the Ti-Ti bonds, there is a concomitant increase in the electrostatic interaction between the dissociated hydrogen atoms and the Ti13 cluster. This enhanced interaction results from the participation of the subsurface titanium atom at higher hydrogen concentrations. Illustrative results of hydrogen saturation on the larger icosahedral Ti55 cluster are also discussed. The importance of these results on hydrogen saturated titanium clusters in elucidating the mechanism of hydrogen adsorption and desorption in titanium doped complex metal hydrides is discussed.     

Structural characterizations and electronic properties of boron nitride nanotube crystalline bundles

The structural characterizations and electronic properties of aligned armchair single-walled boron nitride nanotube (BNNT) bundles are theoretically investigated. In the spontaneous bundling process, the cylindrical shapes of bundled BNNTs are preserved all along, whereas their diameters expand, then shrink, and return back to the initial dimensions. Owing to the nonuniform distribution of positive and negative charges among BNNTs, the multipole interaction in bundles is completely dependent upon the chirality of each BNNT and the arrangement of bundled BNNTs. The effect of intertube coupling on the dispersions of BNNT bundles is demonstrated. Our systematical simulations might be helpful for the understanding of potential applications of BNNT bundles in the nanometer manufacturing techniques such as doping, adsorption, and derivative synthesis.     

Structural, electronic, and vibrational properties of amino-adamantane and rimantadine isomers

We performed a first principles total energy investigation on the structural, electronic, and vibrational properties of adamantane molecules, functionalized with amine and ethanamine groups. We computed the vibrational signatures of amantadine and rimantadine isomers with the functional groups bonded to different carbon sites. By comparing our results with recent infrared and Raman spectroscopic data, we discuss the possible presence of different isomers in experimental samples.     

Borazine-based conjugated derivatives: Structural,electronic, and optical properties

The structural characteristics, electronic properties, and nonlinear optical properties of borazine-based conjugated derivatives have been explored at B3LYP/6-311G(d,p) level. The effects of various electron donor and acceptor substituents (H, F, Cl, Br, Me, CF₃, NH₂, OH, COOH, CHO, NO₂) on the structure, polarizability, frontier orbitals, the most intense electronic transition, and hyperpolarizabilities have studied. Calculations show that NO₂-substituted molecules have lowest hardness, the largest isotropic polarizability and anisotropy of polarizability, and first hyperpolarizability.     

Structural and electronic properties of defective 2D transition metal dichalcogenide heterostructures

We present a first-principles study on the structure-property relationships in MoS₂ and WS₂ monolayers and their vertically stacked hetero-bilayer, with and without Sulfur vacancies, in order to dissect the electronic features behind their photocatalytic water splitting capabilities. We also benchmark the accuracy of three different exchange-correlation density functionals for both minimum-energy geometries and electronic structure. The best compromise between computational cost and qualitative accuracy is achieved with the HSE06 density functional on top of Perdew–Burke–Ernzerhof minima, including dispersion with Grimme's D3 scheme. This computational approach predicts the presence of mid-gap states for defective monolayers, in accordance with the present literature. For the heterojunction, we find unexpected vacancy-position dependent electronic features: the location of the defects leads either to mid-gap trap states, detrimental for photocatalyst or to a modification of characteristic type II band alignment behavior, responsible for interlayer charge separation and low recombination rates.