Non-planar Ones Research Articles

HOMA Index Establishes Similarity to a Reference Molecule.

The article shows that the definition of the HOMA index of geometrical aromaticity satisfies the axioms of a similarity function between the examined and benzene ring. Consequently, for purely mathematical reasons, the index works exceptionally well as an index of aromaticity: it expresses a geometric similarity to the archetypal aromatic benzene. Thus, if the molecule is geometrically similar to benzene, then it is also chemically similar, and therefore, it is aromatic. However, the similarity property legitimizes using the HOMA-like indices to express similarity to molecules other than benzene, whether cyclic or linear and existing or hypothetical. The paper demonstrates an example of HOMA-similarity to cyclohexane, which expresses a (relaxed)-saturicity property not accompanied by strong structural strains or steric hindrances. Further, it is also shown that the HOMA index can evaluate the properties of whole molecules, such as 25 unbranched catacondensed isomers of hexacene. The index exhibits a significant quadratic correlation with the total energy differences of planar isomers from which the nonplanar ones deviate. Moreover, the HOMA index of hexacene isomers significantly correlates with the Kekulé count connected to the resonance energy in the Hückel approximation. As a result, the study shows that the HOMA index can be used not only for aromaticity analyses but also as a general chemical descriptor applicable to rings, chains, composed molecular moieties, or even whole molecules.

Effect of non-planar cracks with islands of contact on the elastic properties of materials

The contribution of a spherical cap crack having an “island” of contact between its faces into elastic compliance of a material is analyzed. Vector of the displacement discontinuity at the crack faces in response to remotely applied stress is calculated using the mesh free technique based on the solution approximation by Gaussian functions. The result is used to construct the compliance contribution tensor of this crack as a function of the island position and extent of non-flatness of the crack. This tensor is orthotropic and the two mentioned factors produce complex combined effect. To study these effects, simple analytical approximation for the obtained numerical result is proposed. The effect of position of the contact is substantial even for planar cracks and it becomes much stronger for non-planar ones; the effect of the size of the contact is generally similar to that for planar cracks. Moderately non-planar cracks may be approximated by planar ones with acceptable accuracy.

Exfoliation and re-aggregation mechanisms of black phosphorus: A molecular dynamics study

We used molecular dynamics simulations to extensively investigate the influence of the solvent molecule’s self-diffusion, morphology/size and interaction energies on the exfoliation/re-aggregation mechanisms of black phosphorous (BP). For such a purpose, eight solvents, with a Hildebrand solubility parameter close to that of BP, are tested and then classified as a function of their planarity. In terms of exfoliation ease, planar molecules are found to require less energy than non-planar ones due to their high self-diffusion and strong interaction with phosphorene sheets. This exfoliation process gives rise to a suspension where each phosphorene sheet is surrounded by a surface-molecular dense layer. Then, the stability of this phosphorene suspension is found to be governed by the formation of a confined molecular layer. The energy balance of this confined layer, with respect to that of the surface-molecular layer, is of central importance. When the solvent molecules cohesion energy becomes weaker, with respect to the adhesion energy between phosphorene and molecules, a confined layer is favored then trapped between the phosphorene sheets forming therefore a stabilized system. The higher is the energy interaction of the confined layer, the favorable re-aggregation process is. In this context, non-planar molecules are found unfavorable neither for a stable phosphorene suspension nor for an easy exfoliation process.

Evaluating multi-loop Feynman integrals numerically through differential equations

The computation of Feynman integrals is often the bottleneck of multi-loop calculations. We propose and implement a new method to efficiently evaluate such integrals in the physical region through the numerical integration of a suitable set of differential equations, where the initial conditions are provided in the unphysical region via the sector decomposition method. We present numerical results for a set of two-loop integrals, where the non-planar ones complete the master integrals for gg → γγ and qoverline{q} → γγ scattering mediated by the top quark.

A short review of nanographenes: structures, properties and applications

ABSTRACTGraphene has attracted great interest in the science and technology since it was exfoliated mechanically from the graphite in 2004. Although graphene has various potential applications, its practical applications are constrained enormously by its serious drawbacks, such as zero band gap, tendency of aggregation between layers and hydrophobicity, which mainly caused by the infinite planar hexagonal structure of graphene. Considering that the structural defects in the honeycomb lattice and the edges of graphene break the infinite structure and thus change the properties, which may improve the application efficiency, nanographene (NG) is proposed and attracts extensive attention. In this work, we review the structures of multifarious well-defined NGs synthesised in recent experiments. The effects of the shape, size, edges and substituents of NGs to the properties are discussed in detail and the regulation for various properties of NG is analysed. For the well-defined NGs, including planar and non-planar ones, the challenges and perspectives of their potential applications in nonlinear optical material, gas molecular detector and gas separation material, hydrogen storage material, and hole-transporting material in perovskite solar cells are envisioned.

Nano-scale feature analysis achieving high effective lateral resolution with micro-scale material characterization techniques: Application to back-end processing

Achieving higher performances of electronic devices was first realized by decreasing feature size followed by the introduction of new materials and the switch from planar devices to non-planar ones. Unfortunately, many characterization techniques do not reach lateral resolution compatible with device sizes. This is the case for energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), Rutherford backscattering spectrometry (RBS), or time of flight) secondary ion mass spectrometry (TOF-)SIMS. This, however, does not render these techniques useless for small size analysis. This is demonstrated in separate examples taken from back-end of line processing. In back-end, trenches to be filled with metal lines are etched. This process leaves residues on the surfaces that need to be cleaned. XPS is an adequate technique to analyze the chemical composition of (remaining) surface components but does not have the resolution needed to investigate single lines. By using periodic structures and a mathematical model, the composition of the top, sidewall and bottom of the trenches can be easily identified. Once formed, these trenches need to be filled with metallic copper. Due to the small size of the lines, the copper filling is prone to voids formation, which has to be avoided. A good estimation of the presence of void can be achieved using EDS while, intrinsically, the lateral resolution is typically significantly worse than the line dimensions.

(Invited) High κ/InGaAs for Ultimate CMOS – Interfacial Passivation, Low Ohmic Contacts, and Device Performance

(Invited) High κ/InGaAs for Ultimate CMOS – Interfacial Passivation, Low Ohmic Contacts, and Device Performance

Electronic structure and reactivity in water splitting of the iron oxide dimers and their hexacarbonyls: A density functional study

The iron oxide dimers (FeO)2 and their peroxide isomers are studied with the B3LYP density functional as bare clusters and as hexacarbonyls. Among the bare clusters the planar four-member ring structures are more stable than the non-planar ones and the rhombic dioxide Fe2O2 with antiferromagnetically ordered electrons on iron centers is the global minimum. Water adsorption on the bare diiron dioxide is exothermic, but dissociation does not occur. Carbonylation favors a non-planar Fe2O2 ring for both the dioxides and the peroxides and high electron density at the Fe centers is induced, evidenced by the natural charge distribution, the high proton affinity, and the values of global electronegativity and hardness. The iron dioxide hexacarbonyl Fe2O2(CO)6 is diamagnetic in the state of the global minimum. It is separated from the next low-lying triplet state by a small energy gap of 0.22 eV. Time-dependent density functional theory methods were applied to examine electron excitations from the ground state to the low-lying triplet states in the hexacarbonyls and their adsorption complexes with water. Singlet-to-triplet state excitations occur via ligand-to-metal charge transfer in the hexacarbonyls; in the adsorption complexes excitations from the oxygen lone pairs to the adsorption center also occur and they appear in the IR-visible region. The lowest energy singlet and triplet state reaction paths for water splitting were followed. On the singlet potential energy surface (PES), water splitting is spontaneous, while for the triplet PES an activation barrier of 14.1 kJ mol(-1) was determined.

Roles of Free Radicals in Type 1 Phototherapeutic Agents: Aromatic Amines, Sulfenamides, and Sulfenates

Detailed analyses of the electron spin resonance (ESR) spectra, cell viability, and DNA degradation studies are presented for the photolyzed Type I phototherapeutic agents: aromatic amines, sulfenamides, and sulfenates. The ESR studies provided evidence that copious free radicals can be generated from these N-H, N-S, and S-O containing compounds upon photoirradiation with UV/visible light. The analyses of spectral data allowed us to identify the free radical species. The cell viability studies showed that these agents after exposure to light exert cytotoxicity to kill cancer cells (U937 leukemia cell lines HTC11, KB, and HT29 cell lines) in a dosage- and time-dependent manner. We examined a possible pathway of cell death via DNA degradation by a plasmid cleavage assay for several compounds. The effects of photosensitization with benzophenone in the presence of oxygen were examined. The studies indicate that planar tricyclic amines and sulfenamides tend to form π-electron delocalized aminyl radicals, whereas nonplanar ones tend to yield nitroxide radicals resulting from the recombination of aminyl radicals with oxygen. The ESR studies coupled with the results of cell viability measurements and DNA degradation reveal that planar N-centered radicals can provide higher potency in cell death and allow us to provide some insights on the reaction mechanisms. We also found the formation of azatropylium cations possessing high aromaticity derived from azepines can facilitate secondary electron transfer to form toxic O2(•-) radicals, which can further exert oxidative stress and cause cell death.

Fabrication and Characteristics of ZnO/OAD-InN/PbPc Hybrid Solar Cells Prepared by Oblique-Angle Deposition

In this work, lead phthalocyanine (PbPc) and ZnO/InN inorganic semiconductor films prepared by oblique-angle deposition (OAD) were layered to form heterojunction organic/inorganic hybrid photovoltaic solar cells. Among the available organic materials, phthalocyanines, particularly the non-planar ones such as PbPc, are notable for their absorption in the visible and near infrared regions. The organic/inorganic hybrid solar cells fabricated on ZnO/OAD-InN/PbPc showed short-circuit current density (JSC), open-circuit voltage (VOC), and power conversion efficiencies (η) of 1.2 mA/cm2, 0.6 V and 0.144%, respectively.

Photodegradation of Selected PCBs in the Presence of Nano-TiO2 as Catalyst and H2O2 as an Oxidant

Photodegradation of five strategically selected PCBs was carried out in acetonitrile/water 80:20. Quantum chemical calculations reveal that PCBs without any chlorine on ortho-positions are closer to be planar, while PCBs with at least one chlorine atoms at the ortho-positions causes the two benzene rings to be nearly perpendicular. Light-induced degradation of planar PCBs is much slower than the perpendicular ones. The use of nano-TiO2 speeds up the degradation of the planar PCBs, but slows down the degradation of the non-planar ones. The use of H2O2 speeds up the degradation of planar PCBs greatly (by >20 times), but has little effect on non-planar ones except 2,3,5,6-TCB. The relative photodegradation rate is: 2,2′,4,4′-TCB > 2,3,5,6-TCB > 2,6-DCB ≈ 3,3′,4,4′-TCB > 3,4′,5-TCB. The use of H2O2 in combination with sunlight irradiation could be an efficient and “green” technology for PCB remediation.

Segmentation and Reconstruction of Polyhedral Building Roofs From Aerial Lidar Point Clouds

This paper presents a solution framework for the segmentation and reconstruction of polyhedral building roofs from aerial LIght Detection And Ranging (lidar) point clouds. The eigenanalysis is first carried out for each roof point of a building within its Voronoi neighborhood. Such analysis not only yields the surface normal for each lidar point but also separates the lidar points into planar and nonplanar ones. In the second step, the surface normals of all planar points are clustered with the fuzzy <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</i> -means method. To optimize this clustering process, a potential-based approach is used to estimate the number of clusters, while considering both geometry and topology for the cluster similarity. The final step of segmentation separates the parallel and coplanar segments based on their distances and connectivity, respectively. Building reconstruction starts with forming an adjacency matrix that represents the connectivity of the segmented planar segments. A roof interior vertex is determined by intersecting all planar segments that meet at one point, whereas constraints in the form of vertical walls or boundary are applied to determine the vertices on the building outline. Finally, an extended boundary regularization approach is developed based on multiple parallel and perpendicular line pairs to achieve topologically consistent and geometrically correct building models. This paper describes the detail principles and implementation steps for the aforementioned solution framework. Results of a number of buildings with diverse roof complexities are presented and evaluated.

Equivalent Oxide Thickness of Trigate SOI MOSFETs With High-$\kappa$ Insulators

The evolution of traditional metal-oxide-semiconductor field-effect transistors (MOSFETs) from planar single-gate devices into 3-D ones with multiple gates and high-kappa insulators imposes the use of new electrical models that accurately reproduce their behavior. This paper demonstrates that the typical expression of equivalent oxide thickness (EOT) for planar devices with high- kappa gate insulators becomes useless for nonplanar ones such as triple-gate (trigate) silicon-on-insulator MOSFETs. An alternative expression of the EOT for these trigate devices has been developed through a semianalytical approach to the gate-insulator capacitance. The proposed model correctly reproduces the total electron density in a wide range of device dimensions and applied biases.

SUBSTRATE INTEGRATION OF DUAL INDUCTIVE POST WAVEGUIDE FILTER

Integration of planar circuits to non-planar ones has been recently considered as a credible technique for low-cost mass production of microwave and millimeter-wave circuits andsystems. This paper regards these concepts that provide for a complete integration of planar circuits andwaveguid e filters synthesizedon a single substrate by means of metalizedpost (via-hole) arrays. A methodof d esigning a waveguide filter derived from a synthesis technique using dual array of inductive posts is presented. An experimental five-pole Chebyshev filter which has 2.5 dB insertion loss and return loss better than 10 dB is demonstrated. Such a technique of integration of planar andnon-planar circuits on the same substrate shows a significant reduction in size, weight and cost.

On the molecular conformation of bisaromatic systems the case of 2-phenyl-2 H-benzotriazoles

2-Phenyl-2 H-benzotriazole exhibits a planar molecular conformation both in its ground electronic state (S 0) and its first excited singlet (S 1) and triplet state (T 1). However, introducing one or two methyl groups in the ortho positions of the phenyl ring causes the aromatic systems in the compound to lose their coplanarity in both S 0 and T 1 electronic states. On the other hand, 2-(2-methylphenyl)-2 H-benzotriazole regains such coplanarity in its first excited singlet state S 1, giving rise to population inversion that could be used to generate stimulated radiation around 350 nm. As shown in this work, the effectiveness of the ISC process in these compounds is markedly dependent on the twisting angle, θ, of the structure; accordingly, ISC occurs to a negligible extent in a planar compound such as 2-phenyl-2 H-benzotriazole, where θ = 0°. This evidence supports the assumption that planar molecular forms of the TIN-P photoprotectors are more photostable than non-planar ones due to the non effective generation via ISC of their triplet states.

Fabrication of Planar Nano-gap Electrodes for Single Molecule Evaluation

This paper aims is to fabricate planar nano-gap electrodes for single molecule characterization, which allow to measure the intrinsic nature of single molecule and to derive the number of molecules on them by atomic force microscopy (AFM), whereas conventional non-planar ones do not. Thus, the planar nano-gap electrodes are the essential tool for single molecule electronics research. Currently, the fabrication technology by anodic bonding realized planar electrodes with 300 nm in width and 200 nm in length. Insulation characteristics of the fabricated electrodes were evaluated and were in the order of 1012 Ω, which indicates that these electrodes are suitable for single molecule evaluation.

Single Molecule Spectroscopy as a Probe for Dye−Polymer Interactions

Experimental (Single Molecule Spectroscopy) and theoretical (quantum-chemical calculations and Monte Carlo and molecular dynamics simulations) techniques are combined to investigate the behavior and dynamics of a polymer-dye molecule system. It is shown that the dye molecule of interest (1,1'-dioctadecyl-3,3,3',3'-tetramethylindo-dicarbocyanine) adopts two classes of conformations, namely planar and nonplanar ones, when embedded in a poly(styrene) matrix. From an in-depth analysis of the fluorescence lifetime trajectories, the planar conformers can be further classified according to the way their alkyl side chains interact with the surrounding poly(styrene) chains.

MP2 and DFT studies of the DNA rare base pairs: The molecular mechanism of the spontaneous substitution mutations conditioned by tautomerism of bases

We investigated structures and electronic properties of DNA base pairs containing the lactim forms of guanine (G*) or thymine (T*) as well as the imino forms of cytosine (C*) or adenine (A*) by ab initio MP2 and DFT methods. The found stable structures of G*–T and G–T* base pairs are the nonplanar ones. The obtained formation energies indicate that G*–T and A–C* are more favorable than G–T* and A*–C. The nature of their hydrogen bonding was discussed based on the energy decomposition analysis of Morokuma–Kitaura and the reduced-variational-space methods to elucidate the possibility of the tautomerization of DNA base pairs.

Surface Waves in a Square Container Due to Resonant Horizontal Oscillations

Resonantly forced water waves in a square container due to its horizontal oscillations are examined. The excited waves are assumed to be gravity waves for infinite depth. Using the reductive perturbation method and including the effect of a linear damping, we derive an evolution equation for the complex amplitudes of two degenerate resonant modes. When the angle θ between the direction of the oscillations and that along one of the sidewalls of the container is 0° or 45°, we obtain planar stationary solutions without the rotation of wave pattern as well as a pair of non-planar ones associated with the clockwise or anti-clockwise rotation. If 0° < θ< 45° , however, no planar stationary solution exists, and the symmetry between these non-planar solutions for θ=0° or 45° is broken. We find the pitchfork bifurcations of the stationary solution for θ=0° and 45°, and also the Hopf and saddle-node bifurcations of this solution for 0° ≤θ≤45°. Furthermore, periodic or chaotic solutions exist within the parameter re...

Formation of Al Clusters Grown on the Hydrogenated Diamond Surfaces

Stable structures of Al clusters grown on completely or incompletely H-terminated diamond (111) surfaces have been determined by first principles quantum chemical calculations. When Al atoms are deposited on the completely H-terminated diamond surface, planar stable structures are possibly formed as well as nonplanar ones. On the other hand, only nonplanar type Al clusters are grown on the partly H-removed surface losing three H atoms from the complete H-termination, and those nonplanar Al clusters have the structure of a single Al crystal. The result suggests the possibility of an epitaxial growth of Al metals on the diamond (111) substrate.