Mixed Character Research Articles

Unveiling the optical parameters of vanadium dioxide in the phase transition region: a hybrid modeling approach.

The phase change behavior of vanadium dioxide (VO2) has been widely explored in a variety of optical and photonic applications. Commonly, its optical parameters have been studied in two extreme regimes: hot (metallic) and cold (insulating) states. However, in the transition temperatures, VO2 acts like an inherent metamaterial with mixed metallic-insulating character. In this range, the portions of metallic and insulating inclusions are tuned by temperature, and therefore a gradual change of optical parameters can be achieved. In this paper, a universal hybrid modeling approach is developed to model VO2 in the intermediate region. For this aim, the measured reflectivity data, is analyzed and matched through the transfer matrix method (TMM) simulations where an effective medium theory (EMT) is employed. Based on the findings of this approach, not only the relative portions of inclusions are tailored but also their grain shapes are significantly altered in the transition range. Finally, the modeling approach is testified by experimental findings through dynamic device applications operating at short and mid infrared wavelengths. In addition, the hysteretic behaviors on electrical, optical, and structural parameters of the VO2 film along the heating and cooling cycles are demonstrated by the experiments and scrutinized by the simulations.

Influence of 4f filling on electronic and magnetic properties of rare earth-Au surface compounds.

One-atom-thick rare-earth/noble metal (RE-NM) compounds are attractive materials to investigate two-dimensional magnetism, since they are easy to synthesize into a common RE-NM2 structure with high crystal perfection. Here we perform a comparative study of the GdAu2, HoAu2, and YbAu2 monolayer compounds grown on Au(111). We find the same atomic lattice quality and moiré superlattice periodicity in the three cases, but different electronic properties and magnetism. The YbAu2 monolayer reveals the characteristic electronic signatures of a mixed-valence configuration in the Yb atom. In contrast, GdAu2 and HoAu2 show the trivalent character of the rare-earth and ferromagnetic transitions below 22 K. Yet, the GdAu2 monolayer has an in-plane magnetic easy-axis, versus the out-of-plane one in HoAu2. The electronic bands of the two trivalent compounds are very similar, while the divalent YbAu2 monolayer exhibits different band features. In the latter, a strong 4f-5d hybridization is manifested in neatly resolved avoided crossings near the Fermi level. First principles theory points to a residual presence of empty 4f states, explaining the fluctuating valence of Yb in the YbAu2 monolayer.

Hyperfine structure of the NaCs b3Π2 state near the dissociation limit 3S1/2 + 6P3/2 observed with ultracold atomic photoassociation.

We report new observations of the hyperfine structure in three ro-vibrational levels of the b3Π2 state of NaCs near the dissociation limit 3S1/2 + 6P3/2. The experiment was done via photoassociation of ultracold atoms in a dual-species dark-spot magneto-optical trap, and the spectra were measured as atomic trap losses. The simulation of the hyperfine structure showed that the greater part of the observed structure belongs to almost isolated levels of the b3Π2 state, but there are other parts of mixed character where the contribution from the 1Σ symmetry dominates.

First-principles soft-mode lattice dynamics of PbZr0.5Ti0.5O3 and shortcomings of the virtual crystal approximation

A comparative study between PbTiO$_3$, PbZrO$_3$, and the solid solution PbZr$_{0.5}$Ti$_{0.5}$O$_3$ is performed on the soft mode lattice dynamics within the first Brillouin Zone. We consider the six unique B-site orderings for PbZr$_{0.5}$Ti$_{0.5}$O$_3$ representable within the 2$\times$2$\times$2 primitive perovskite supercell as well as the virtual crystal approximation (VCA) to extract the phonon dispersion relations of a high-symmetry cubic-constrained form using density functional perturbation theory. We find that the most unstable modes in the rock-salt ordered structure and the VCA, like pure PbZrO$_3$, are antiferrodistortive (AFD) whilst lower symmetry arrangements are dominated by $\Gamma$-point ferroelectric (FE) instabilities like pure PbTiO$_3$. Despite similarities in the phonon dispersion relations between the rock-salt ordered supercell and the VCA, the character of modes at high symmetry points are found to be different. In particular, the a$^{0}$a$^{0}$c$^{-}$ & a$^{0}$a$^{0}$c$^{+}$ AFD instabilities of the rock-salt ordering are replaced with a$^{-}$b$^{-}$c$^{-}$ & a$^{+}$b$^{+}$c$^{+}$ instabilities within the VCA. Such a rotation pattern is not seen in any of the supercell-based calculations thus serving as a quantitative example of the inability of the method to represent accurately local structural distortions. Single modes are found exhibiting dual order parameters. At the zone centre, some arrangements show mixed FE & antipolar soft modes (due to Pb motion tansverse to the polar axis) and at long wavelengths all arrangements have soft modes of a mixed antipolar & AFD character. These are described with direct analysis of the eigendisplacements.

Exploring the Convective Core of the Hybrid δ Scuti-γ Doradus Star CoRoT 100866999 with Asteroseismology

Abstract We computed a grid of theoretical models to fit the δ Scuti frequencies of CoRoT 100866999 detected earlier from the CoRoT time serials. The pulsating primary star is determined to be a main-sequence star with a rotation period of days, rotating slower than the orbital motion. The fundamental parameters of the primary star are determined to be , , , K, , , , and , matching those obtained from the eclipsing light-curve analysis. Based on the model fittings, p 1 and p 5 are suggested to be two dipole modes, and p 3, p 4, p 6, and p 7 are suggested to be four quadrupole modes. In particular, p 4 and p 7 are identified as two components of one quintuplet. Based on the best-fitting model, we find that p 1 is a g mode and the other nonradial modes have pronounced mixed characters, which give strong constraints on the convective core. Finally, the relative size of the convective core of CoRoT 100866999 is determined to .

Coherent charge-phonon correlations and exciton dynamics in orthorhombic CH3NH3PbI3 measured by ultrafast multi-THz spectroscopy.

We use time-resolved multi-terahertz spectroscopy for the range 4-40 meV to probe coherent and incoherent ultrafast charge carrier and exciton dynamics in the low temperature orthorhombic phase of the hybrid metal halide perovskite CH3NH3PbI3. Time- and energy-resolved terahertz reflectivity maps reveal strongly damped but coherent oscillations in the 2-4 THz reststrahlen band, indicating charge coupling to a distribution of low energy phonon modes centered at 0.9 THz (3.7 meV or 30 cm-1). First-principles calculations reveal that these modes are entirely of mixed organic/inorganic sublattice character, with the power spectrum of the coherent oscillations showing a high frequency cutoff just at the onset of organic cation-only vibrations. Two anomalous reflectivity signatures are observed which are not phonon related, which we assign to a free exciton at 12 meV appearing on a 0.5 ps time scale and a defect bound exciton at 29-32 meV appearing on slower 1 ps time scale. Our measurements reveal the coherent coupling of charges to low energy vibrations of mixed sublattice character and the presence of two distinct populations of free and bound excitons at low temperatures.

About Bracelets with Zoomorphic Ends from Dzhurga-Oba Necropolis in Eastern Crimea (Great Migration Period)

The paper considers burial 40 of Dzhurga Oba necropolis in the Eastern Crimea. Two bracelets, elements of a prestigious female costume of the second half of the 5th century and weapons (sword elements) were found in the catacomb. It is possible that there were two inhumations – male and female ones. Two bronze gilded bracelets from this burial have gold zoomorphic endings in the form of heads, usually interpreted as dragons, and a hinged lock in the form of a disk. The origins of this type of bracelets should be sought in the traditions of Mediterranean jewelry art. Bracelets with a lock in the form of a plate on hinges appeared in the Mediterranean in the 2nd – 3rd centuries and existed until the 7th century (inclusive). It should be noted that there is a noticeable Byzantine / Mediterranean component in the female costume from Dzhurga Oba, which is represented primarily by the cloisonne inlay style jewelry – earrings, rings, bracelets. At the same time, the presence of a pair of brooches from the East German tradition indicates the mixed character of the female prestigious costume from Dzhurga-Oba, which is typical for the Cimmerian Bosporus of the Great Migration Period.

The Bastar craton, central India: A window to Archean – Paleoproterozoic crustal evolution

The Bastar craton in central India, surrounded by cratonic blocks and Paleoproterozoic to Neoproterozoic orogenic belts, is a window to investigate the Archean-Paleoproterozoic crustal evolution and tectonic processes. Here we propose a new tectonic classification of the craton into the Western Bastar Craton (WBC), Eastern Bastar Craton (EBC), and the intervening Central Bastar Orogen (CBO). We present petrologic, geochemical and zircon U-Pb, REE and Lu-Hf data from a suite of rocks from the CBO and along the eastern margin of the WBC Including: (1) volcanic successions comprising meta-andesite and fine-grained amphibolite, representing arc-related volcanics along a convergent margin; (2) ferruginous sandstone, in association with rhyolite, representing a volcano-sedimentary succession, deposited in an active trench; and (3) metamorphosed mafic-ultramafic suite including gabbro, pyroxenite and dunite invaded by trondhjemite representing the section of sub-arc mantle and arc root adjacent to a long-lasting subduction system. Petrologic studies indicate that the mafic-ultramafic suite crystallized from an island arc tholeiitic parental magma in a suprasubduction zone environment. The chondrite-normalized and primitive mantle normalized diagrams of the mafic and ultramafic rocks suggest derivation from MORB magma. The mixed characters from N-MORB to E-MORB of the studied samples are consistent with subduction modification of a MORB related magma, involving partial melting of the metasomatized mantle wedge. Our zircon U-Pb age data suggest that the cratonic nuclei was constructed as early as Paleoarchean. We present evidence for active subduction and arc magmatism through Mesoarchean to Neoarchean and early Paleoproterozoic, with the trench remaining open until at least 2.3 Ga. Two major crust building events are recognized in the Bastar craton: during Mesoarchean (recycled Paleoarchean subduction-related as well as juvenile/depleted mantle components) and Neoarchean (accretion of juvenile oceanic crust, arc magmatism including granite batholiths and related porphyry mineralization). The final cratonization occurred during latest Paleoproterozoic, followed by collisional assembly of the craton and its incorporation within the Peninsular Indian mosaic during Mesoproterozoic. In the global supercontinent context, the craton preserves the history of Ur, the earliest supercontinent, followed by the Paleo-Mesoproterozoic Columbia, as well as minor thermal imprints of the Neoproterozoic Rodinia and associated Grenvillian orogeny.

Effects of strain on electronic and optical properties of LiNbO3: a first principles study

The exchange-correlation functions of local density approximation and generalized gradient approximation using density functional theory were performed to calculate electronic and optical properties of lithium niobate crystal. To correct the underestimated value of band gap, a reverse scissor correction procedure was performed based on the experimental refractive index value because it is more suitable for compound with polar crystal. It is found that underestimated electronic band gap ∼4.76 eV was generated due to nature of generalized gradient approximation (GGA) exchange correlation. Based on density of states calculation, Li ion tends to diffuse into substrate as it possesses pure ionic character. Thus, the chemical bonding in LiNbO3 crystal has a mixed covalent-ionic character. The effect of strain on a-axis of the crystal and thus, its electronic and optical properties were investigated. The a-axis of the crystal is more sensitive towards the strain compared to c-axis as the band gap largely changes upon the applied strain. The optical properties such as dielectric function, refractive index, extinction coefficient, and absorption were calculated and explained in detail. The positive and negative strains do shift the optical spectrum either to higher or lower frequency depending on specific properties. These results would assist to provide the fundamental explanation about the effect of strain on the properties of lithium niobate crystal.

Negative piezoelectric response of van der Waals layered bismuth tellurohalides

The polarization and piezoelectric response of the BiTe$X$ ($X$=Cl, Br, and I) layered tellurohalides are computed from first principles. The results confirm a mixed ionic-covalent character of the bonding, and demonstrate that the internal structure within each triple layer is only weakly affected by the external stress, while the changes in the charge distribution with stress produce a substantial negative piezoelectric response. This suggests a new mechanism for negative piezoelectric response that should remain robust even in ultra-thin film form in this class of materials.

Engineering the optical and electronic properties of (AlN)1/(ZnO)1 superlattice by bi-axial stresses

In order to analyze both the electronic and optical properties of the (AlN)1/(ZnO)1 superlattice under biaxial strains, we report here, first-principles calculations within the density functional theory framework. As a result, lattice parameters, as well as band gap values, are found in overall good agreement with available experimental data. Additionally, calculation coming from the prediction of elastic calculation and phonon spectra shows that the title material is thermodynamically stable in the wurtzite structure. Due to the mixing character of (AlN)1/(ZnO)1 in its bonding pattern, the tensile regime shows a weak influence on the electronic properties. However, the compression regime affects strongly the band gap and its nature. Overall, the absorption coefficient shows a serious change under bi-axial strains, making the (AlN)1/(ZnO)1 material promising for ultraviolet–visible sensor applications.

Results of morphological diagnosis of the aetiology of the diffuse lung disease syndrome.

Background. Diffuse Pulmonary diseases (DZL) is a heterogeneous group of diseases united on the basis of the characteristic radiological syndrome of pulmonary dissemination, which is manifested by widespread changes in both lungs of nodular, reticulate or mixed character with nonspecific clinical and altered pathological changes. Objective. To present the results of morphological diagnostics of the pathological process in the syndrome of pulmonary dissemination and to compare them with the final clinical diagnoses when applying different methods of biopsy sampling. Methods. 216 lung biopsies were selected for morphological diagnosis, followed by histological examination in 210 patients. Patients were divided into 4 groups depending on the method of obtaining biopsy material for histological examination (video assisted, open and transbronchial lung biopsy). Results. Most patients were with sarcoidosis 81 (37.5 ± 3.3)%metastatic lung damage was diagnosed for 36 (16.7 ± 2.5)% cases. Other diseases (various forms of fibrotic alveolitis, alveolar proteinosis, histiocytosis, diffuse pulmonary ossification, etc.) 25 (11.6 ± 2.2)% and pulmonary tuberculosis – 24 (11.1 ± 2.1) % cases. Conclusion. Prevalent patients were diagnosed with "disseminated process in lungs of unknown etiology" – 121 (57,6 ± 3,4)% of patients and "diffuse process in lungs in combination with syndrome of intrathoracic lymphadenopathy" – 41 (19,5 ± 2,7)% patient. According to the histological examination, sarcoidosis was the most common in 81 (37.5 ± 3.3)% of cases and metastatic lung injury was 36 (16.7 ± 2.5)%; Morphological examination of the pulmonary tissue in the case of pulmonary dissemination syndrome reveals numerous diseases of different etiology; or "narrows" the spectrum of pathology in the differential diagnosis of a particular disease.

A Novel Linear Antenna Synthesis for Linear Dispersion Codes Based on an Innovative HYBRID Genetic Algorithm

As far as taking-away of the symmetry constraints is concerned, as a scientifically symmetry problem, the global synthesis for antenna arrays that produce the desired radiation pattern is also a highly nonlinear optimization issue in fact. Besides this, the built criteria offer the reasonable power patterns. The consequent synthesis could be implemented by looking for a nominal pattern. When the criteria are already sufficient, it can simply do the whole synthesis process. To utilize multiple antennae, a method to choose a transmit antenna for the linear dispersion codes (LDC-TAS) is implemented in this paper. The authors used the max–min-post- signal to noise ratio (SNR) criteria to select these optimal transmitting antennae while this dependent, linear receiver is applied to the varying and slow channel. The simulated results illustrate that this max–min-post-SNR criterion outperforms the Bell Labs layered space time transmitting antenna selection (BLAST-TAS) applying the same spectral efficiency than space–time block codes (STBC)-TAS in the environment with low SNR. Furthermore, once the M antennae are selected under the selection criteria, a max–min-post-SNR rule, a novel linear antenna synthesis to linear dispersion codes on the basis of an innovative HYBRID (of mixed characters or solutions) genetic algorithm has been presented and evaluated to formulate and address the optimal problem to non-uniformly spaced and linear arrays. The restricted side-lobes level, the main-lobe width, and the shaped beam pattern are contemporarily concerned via maximizing a pretty suitable cost function through the innovational advanced genetic-algorithm-based algorithm. The method proposed in this paper can provide flexibility and a simple insertion of the a priori knowledge under a small computing pressure. At last, a computing simulation is completed well and the results are shown. It should be noticed that some extensions of the presented method could also be easily utilized without an obvious increase in the algorithm complexity.

The effect of diffusion-mobile and combined hydrogen on hydrogen brittleness of steel

Diagnostics of the emergencies attributed to the pipeline destruction resulted from hydrogen charging and corrosion is one of the important problems of the oil and gas industry. Corrosion and hydrogen charging of the metal lead to formation of holes in the pipe wall at a certain critical ratio of the metal strength and thickness resulted from the impact of the internal pressure of the gas transported through the pipeline. Despite extensive research, many issues related to this problem require further consideration. This concerns, in particular, the issues regarding kinetics of the brittle fracture of metal of the pipeline walls and the role of diffusion-mobile (active) and combined (bound) hydrogen in this process. Electrochemical hydrogenation (saturation) of cylindrical steel samples revealed that the zone of penetration of electrolytic hydrogen match the region of the cleavage crack origin, i.e., the area of the subsurface hydrogen distribution can be considered a local area of micro-cleavage in the peel tests thus making possible the study of kinetics and concentration dependences of steel brittle fracture under the impact of both diffusion-mobile and combined hydrogen, i.e., under conditions of reversible and irreversible hydrogen brittleness. The dependences of the peel resistance (micro-cleavage) on the concentration of diffusion-mobile (active) and bound hydrogen in the micro-cleavage zone are obtained as a result of kinetic studies. Electron-fractographic study of fractures of 18KhGMF steel samples showed that fracture morphology changes in accordance with the stages of brittleness development. The initial ductile fracture is followed by a typically brittle peeling at reversible brittleness. Then, with the development of irreversible fragility, a mixed character of destruction is observed. The obtained three-stage dependence of the peeling strength, taking into account different hydrogen states, proves the different physical nature of the processes at different stages of hydrogen brittleness and connects the known reversible and irreversible hydrogen brittleness with the effect of diffusion-mobile and bound hydrogen, respectively.

Continuum model for the core of a straight mixed dislocation

Linear elasticity theory predicts a divergent strain field at the dislocation core, resulting from the continuum approximation breaking down at the atomic scale. We introduce a minimum model that includes elastic interactions and discrete lattice periodicity, and derive a set of equations that treat the core of an edge dislocation from a solely geometric perspective. We find an analytical formula for the displacement field of a straight dislocation of arbitrary mixed character, and we predict that the dislocation core widens as the screw character becomes more dominant. This finding is in qualitative and quantitative agreement with atomistic simulations of mixed dislocations in tungsten. The theory is based on a continuum form of the multistring Frenkel-Kontorova model, which is a nearest-neighbor model for atomic bonding that also takes into account the discreteness of the crystal lattice. Thus, we circumvent the need to use adjustable parameters in the treatment of a dislocation core.

Wet Cleaning by Using Amphoteric Electrolyzed Water for Mask Cleaning

Process achievement for manufacturing extreme ultraviolet(EUV) semiconductor device requires profound technical varieties such as extreme extension of the existing concepts or new evolutional ones. In this study, a new technology was proposed to fulfill technical details required for EUV semiconductor device cleaning and manufacturing. The special electrolysis technology of ultrapure water(UPW) was introduced to generate water possessing quite unexpectedly mixed character such as pH of 6.5 to 6.7 and oxidation reduction potential(ORP) of -540 to –560 mV at room temperature. Since ORP of –550 mV lasted for several days, it was postulated that water clustering reaction due to hydrogen bond could hinder or retard recombination of H+ and OH- ions by synchronously isolating them electronically and physically. This amphoteric water was applied to cleaning process of EUV device manufacturing to carry out the experiment requiring eventually no chemical use for wet cleaning because of 10 nm feature size. Some results were so excellent that it was convinced that this water clean was evolutional to meet EUV requirements. This water did eliminate adsorbed leftovers of previous chemical treatments and minimized surface modifications because of non-chemical character so that it did not provide any chance of haze formation. Since particle removal efficiency(PRE) was very high, it was proposed that there might be other cleaning mechanism than double layer repulsion(DLR) of colloids. Conclusively, it is time to review the conventional wet cleaning technology and to adopt new concept of the amphoteric water to realize the cleaning technology of EUV device era.

Formation mechanism of lamellar alpha in titanium through accurate simulation

The lamellar α, transformed β matrix and spheroidization products of them combine to form all typical microstructures in titanium alloys. Accurately predicting the formation of lamellar α and revealing the precipitation mechanism therefore become vital for tailoring the microstructure and thus optimizing the properties of titanium alloys. A mixed-mode model combined with cellular automaton is proposed to simulate the process of nucleation and growth of lamellar α phase in isothermal treatment of Ti alloys. In this model, the driving force that is dependent on temperature, the solute concentration in two phases and interface is derived; the soft impingement effect, considering the microscopic morphology evolution of lamellar α phase in two dimensions, is well described by not only approximating the diffusion field function in front of the interface as a polynomial but also introducing the area and interface length of lamellar α into the mass conservation law. A comparision with the interface-controlled and diffusion-controlled models shows that the mixed-mode model gives obviously more accurate description of β-to-α phase transformation kinetics. Furthermore, it is also found that the interfacial migration coefficient, and the microscopic morphology of lamellar α phase to be precipitated have great effects on the mixed mode character (in especial the change in controlled mode) and the kinetics of entire phase transformation process.

The Endofullerene HF@C60: Inelastic Neutron Scattering Spectra from Quantum Simulations and Experiment, Validity of the Selection Rule, and Symmetry Breaking.

Accurate quantum simulations of the low-temperature inelastic neutron scattering (INS) spectra of HF@C60 are reported for two incident neutron wavelengths. They are distinguished by the rigorous inclusion of symmetry-breaking effects in the treatment and having the spectra computed with HF as the guest, rather than H2 or HD, as in the past work. The results demonstrate that the precedent-setting INS selection rule, originally derived for H2 and HD in near-spherical nanocavities, applies also to HF@C60, despite the large mass asymmetry of HF and the strongly mixed character of its translation-rotation eigenstates. This lends crucial support to the theoretical prediction made earlier that the INS selection rule is valid for any diatomic molecule in near-spherical nanoconfinement. The selection rule remains valid in the presence of symmetry breaking but is modified slightly in an interesting way. Comparison is made with the recently published experimental INS spectrum of HF@C60. The agreement is very good, apart from one peak for which our calculations suggest a reassignment. This reassignment is consistent with the measured INS spectrum presented in this work, which covers an extended energy range.

Multi-Length Scale Characterization of Microstructure Evolution and Its Consequence on Mechanical Properties in Dissimilar Friction Stir Welding of Titanium to Aluminum

In dissimilar friction stir welding (FSW), the weld nugget is composed of two elements, which are mechanically mixed. This microstructure helps enhance the mechanical properties when they are homogeneously mixed, and the particles are sub-micron in size. Therefore, it is important to understand the mechanism of the particle formation and their distribution for engineering the mechanical properties of the weld. In the present investigation, dissimilar FSW between commercial purity Al and Ti has been carried out. The weld nugget consisted of distributed Ti particles in an Al matrix. The distribution of the Ti particles in the weld nugget was characterized using X-ray micro-computed tomography (XCT). Microstructural evolution in Ti and Al was examined using a scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS), X-ray diffraction and electron back-scattered diffraction (EBSD). Hardness and tensile tests were carried out to determine the integrity of the welds. The XCT result shows that the weld nugget contains Ti particles of variable size. The finer particles of Ti are distributed homogeneously in the weld nugget, unlike large particles. The deformation mechanisms and microstructural evolution of the Ti interface and Al matrix are investigated using EBSD. It is observed that the microstructure of both Ti and Al is substantially refined. However, for a given grain in Al, the boundary is of mixed character, namely low- and high-angle boundaries. Hardness data of the weld indicate large variation within the nugget region. The tensile test sample revealed that the failure of the sample occurs on the Al side of the weld. The fractograph indicates ductile and brittle modes of fracture with a bimodal distribution of dimples at the surface. Lack of twining and fine grains (40 to 5 µm) at the Ti interface indicates high-temperature deformation. Deformation of Ti at low temperature and high strain rate is caused by adiabatic shear banding (ASB). In these shear bands, a high level of grain refinement is observed and is a path for easy crack propagation. It is proposed that the ASB-controlled deformation of Ti leads to a recrystallized microstructure at the interface and fragmentation of Ti. These Ti particles undergo further fragmentation to form smaller particles. On the other hand, microstructural evolution in Al is gradual because of the high stacking fault energy, which leads to continuous dynamic recrystallization (CDRX) through the dynamic recovery (DRV) mechanism. The mechanical properties of the weld depend on the characteristics of particles in the Al matrix. Proper control of the fragmentation and distribution of Ti particles and interface property can lead to superior mechanical properties of the weld.

Halogen and Hydrogen Bonding in Halogenabenzene/NH3 Complexes Compared Using Next-Generation QTAIM.

Next-generation quantum theory of atoms in molecules (QTAIM) was used to investigate the competition between hydrogen bonding and halogen bonding for the recently proposed (Y = Br, I, At)/halogenabenzene/NH3 complex. Differences between using the SR-ZORA Hamiltonian and effective core potentials (ECPs) to account for relativistic effects with increased atomic mass demonstrated that next-generation QTAIM is a much more responsive tool than conventional QTAIM. Subtle details of the competition between halogen bonding and hydrogen bonding were observed, indicating a mixed chemical character shown in the 3-D paths constructed from the bond-path framework set B. In addition, the use of SR-ZORA reduced or entirely removed spurious features of B on the site of the halogen atoms.