Benzene System Research Articles

Molecular Dynamics Simulations of Nanostructures Formed by Hydrophobins and Oil in Seawater.

Classical molecular dynamics simulations using the Martini coarse-grained force field were performed to study oil nanodroplets surrounded by fungal hydrophobin (HP) proteins in seawater. The class I EAS and the class II HFBII HPs were studied along with two model oils, namely, benzene and n-decane. Both HPs exhibit free energy minima at the oil-seawater interface, which is deeper in benzene compared to the n-decane systems. Larger constraint forces are required to keep both HPs within the n-decane phase compared to inside benzene, with HFBII being more affine to benzene compared to EAS. Smaller surface tensions are observed at benzene-seawater interfaces coated with HPs compared to their n-decane counterparts. In the latter the surface tension remains unchanged upon increases in the concentration of HPs, whereas in benzene systems adding more HPs lead to decreases in surface tension. EAS has a larger tendency to cluster together in the interface compared to HFBII, with both HPs having larger coordination numbers when surrounding benzene droplets compared to when they are around n-decane nanoblobs. The HP-oil nanostructures in seawater examined have radii of gyration ranging between 2 and 12 nm, where the n-decane structures are larger and have more irregular shapes compared to the benzene systems. The n-decane molecules within the nanostructures form a compact spherical core, with the HPs partially covering its surface and clustering together, conferring irregular shapes to the nanostructures. The EAS with n-decane structures are larger and have more irregular shapes compared to their HFBII counterparts. In contrast, in the HP-benzene structures both HPs tend to penetrate the oil part of the droplet. The HFBII-benzene structures having the larger oil/HP ratios examined tend to be more compact and spherical compared to their EAS counterparts; however, some of the HFBII-benzene systems that have smaller oil/HP ratios have a more elongated structure compared to their EAS counterparts. This simulation study provides insights into HP-oil nanostructures that are smaller than the oil droplets and gas bubbles recently studied in experiments and, thus, might be challenging to examine with experimental techniques.

Effects of Multiple OH/SH Substitution on the H‐Bonding/Stability versus Aromaticity of Benzene Rings: From Computational Insights

AbstractProperties of intramolecular H‐bond (IHB) for a chemical system can affect the changes in geometrical/electronic features in the vicinity of the bridge. Substitution of an atom (H) in benzene with OH/SH groups forming IHB has little effect on its aromaticity. This report is devoted to the depiction of the effect of OH/SH substituent on stability/aromaticity of multi‐substituted benzene ringsviaIHB formation. The computational studies on the stability/aromaticity in the homo (OH/SH) and hetero (OH and SH) substituted form of the benzene systems have been investigated using B3LYP/aug‐cc‐pVDZ and MP2/aug‐cc‐pVDZ approaches with the aid of aromaticity indices (AIs) descriptors (NICS, HOMA, AIBIC, and PDI) and IHB/stability diagnostics; relative energy, QTAIM based interaction energy acquired from the potential energy density and electron density, HBSBIC, and HOMO‐LUMO gap including NCI plots. The IHBs formed by different OH/SH substituents have a vital role as an aromaticity modulator and deploying the above‐said tools, it turns out that the cyclic 4n+2 π‐electrons delocalization is weakened/strengthened depending on the number and types of OH/SH substituents forming the IHBs. Here, all the AIs vary in a small amount and indicative of the modulator of the π‐electron structure to the substituent effectviaIHB formation. As in practical applications, the diagnostics based on different criteria do not speak with the same voice, hence interestingly, in many cases, the changes in AIs notably correlate with their stability.

Molecular Interactions and Thermophysical Properties of 1, 4 Dioxane with Bromo benzene, Ethyl benzene at various Temperatures via Nonlinear Model

Viscosities and densities of 1,4 dioxane with hydrocarbon bromo benzene, ethyl benzene was measured over the entire mole fractions at temperatures ranging from 303.15, 308.15, and 313.15K. From these experimental results, excess molar volume VE and viscosity deviation ∆η was calculated. The VE and Δη exhibited positive and negative values, respectively, over the entire composition range in the order of 1,4 dioxane+ bromo benzene and < 1,4 dioxane +ethyl benzene systems. The outcomes indicated the weak interactions present in the mixtures. It exists mainly because of the number and position of methyl groups in these aromatic hydrocarbons. The molecular dynamics simulation studies for both the mixtures show no phase separation. The volume occupied by 1,4 dioxane + bromo benzene is lesser than 1,4 dioxane + ethyl benzene substantiating the experimental results of VE and Δη. Standard deviations from the Jouyban–Acree model between the fitting outcomes, and the calculated data are helpful deliberate mixing behavior of the binary mixtures. The molecular interactions existing between the components and comparison of liquid mixtures were also discussed.

Imidazole-based ionogel as room temperature benzene and formaldehyde sensor.

A room temperature benzene and formaldehyde gas sensor system with an ionogel as sensing material is presented. The sensing layer is fabricated employing poly(N-isopropylacrylamide) polymerized in the presence of 1-ethyl-3-methylimidazolium ethyl sulfate ionic liquid onto gold interdigitated electrodes. When the ionogel is exposed to increasing formaldehyde concentrations employing N2 as a carrier gas, a more stable response is observed in comparison to the bare ionic liquid, but no difference in sensitivity occurs. On the other hand, when air is used as carrier gas the sensitivity of the system towards formaldehyde is decreased byone order of magnitude. At room temperature, the proposed sensor exhibited in air higher sensitivities to benzene, at concentrations ranging between 4 and 20ppm resulting, in a limit of detection of 47ppb, which is below the standard permitted concentrations. The selectivity of the IL towards HCHO and C6H6 is demonstrated by the absence of response when another IL is employed. Humidity from the ambient air slightly affects the resistance of the system proving the protective role of the polymeric matrix. Furthermore, the gas sensor system showed fast response/recovery times considering the thickness of the material, suggesting that ionogel materials can be used as novel and highly efficient volatile organic compounds sensors operating at room temperature.Graphical abstract.

New Indolo[3,2-b]indole based small organic molecules for Organic Thin Film Transistors (OTFTs): A combined experimental and DFT Study

Synthesis of new indolo[3,2-b]indoles (5a- 5j) in presence of Ag-doped ZnO and (Diacetoxyiodo) benzene system under visible-light have been reported. All the new fused linear heterocyclic indolo[3,2-b]indole systems (5a- 5j) thoroughly characterized by spectroscopic methods like mass, UV-visible, NMR and C, H, N elemental analysis. Further, their photophysical properties were carried out by combined experimental and theoretical studies. Thermogravimetric studies are carried out to confirm the thermal stability of molecules. The frontier molecular orbitals of molecules are characterized with the help of cyclic voltammetry. Additionally, the compounds of series 5 were used for the fabrication of organic thin-film transistors, which indicated the hole mobilities in the range of 0.11 – 0.85 cm2/Vs and with on/off ratio 105 on ODTS-SiO2 substrate at 50 °C and are also supported by DFT studies.

Accounting for quadrupolar interactions in the CPA equation of state: A modelling approach for binary mixtures of CO2 or benzene with n-alkanes and 1-alkanols

The Cubic Plus Association (CPA) equation of state (EoS) is extended with the theory for quadrupolar molecules of Gross, yielding the CPA-G model. CPA-G is compared to the recently developed qCPA, which uses the polar theory of Larsen and coworkers. Each model requires an additional adjustable parameter for quadrupolar molecules.The models are evaluated by means of their ability to model the phase equilibria of binary mixtures of CO2 or benzene with n-alkanes and 1-alkanols, as well as binary mixtures of quadrupolar molecules. A refined technique of accounting for cross-association in the CO2 + 1-alkanol systems is proposed, allowing an improved description of these systems without the use of a binary interaction parameter. Accounting for cross-association in the benzene + 1-alkanol systems investigated in this work did not lead to improved results. Both CPA-G and qCPA provide significant improvements over nonpolar CPA in both n-alkane and 1-alkanol mixtures, with excellent results obtained in the subcritical region without the use of binary interaction parameters. qCPA continues to provide excellent predictions in the supercritical region, while CPA-G overestimates the solubility pressures in the supercritical region. Both quadrupolar models can qualitatively predict the existence of three-phase equilibrium in the CO2 + n-alkane and CO2 + 1-alkanol systems. The simple combining rules used for cross-quadrupolar interactions in both CPA-G and qCPA do not take molecular orientation into account and are unable to truly capture the phase behaviour in the CO2 + benzene system.

Formation of spiral microstructures during crystallization of 4,4‘-azoxyanisole from a benzene solution

A phenomenon of formation of multiple “coffee rings” consisting of microcrystals in the 4,4‘-azoxyanisole - benzene system was experimentally and theoretically investigated. It is shown that by changing of the geometry of a drop, for example, by placing a metal ball in its center it is possible to fundamentally change the geometry of the “coffee ring”. Assumptions were made about the physical nature of the effect of the formation of a “coffee ring” of a spiral shape. The proposed geometric model of this phenomenon reflects well the physical processes occurring during spiral crystallization, and the model is in good agreement with the experimental data obtained by gravimetry. New approaches to the formation of microstructures of functional materials with a thermotropic liquid crystal phase on a glass substrate can be used to create devices for nano – and microelectronics and optical technology.

Influence of Fresh Oil on the Performance of Circulating Absorbent Oil in Benzene Processing

Abstract—In changing the composition of coking batch, it is expedient also to ensure effective operation of the benzene department, both in terms of the production of commercial phenolic hydrocarbons and in order to maintain normal operation of the coke batteries’ heating system. In assessing the fresh absorbent oil used to replenish the circulating oil, not only its operational characteristics must be taken into account but also its influence on the performance of the absorbent already in the system. The introduction of low-molecular components in the circulating absorbent oil intensifies the extraction of hydrogen sulfide from the coke-oven gas in the benzene department. In selecting the composition and properties of the circulating absorbent oil, the operation of the specific benzene system and the overall gas channel must be taken into account.

Multi-generation OH oxidation as a source for highly oxygenated organic molecules from aromatics

Abstract. Recent studies have recognised highly oxygenated organic molecules (HOMs) in the atmosphere as important in the formation of secondary organic aerosol (SOA). A large number of studies have focused on HOM formation from oxidation of biogenically emitted monoterpenes. However, HOM formation from anthropogenic vapours has so far received much less attention. Previous studies have identified the importance of aromatic volatile organic compounds (VOCs) for SOA formation. In this study, we investigated several aromatic compounds, benzene (C6H6), toluene (C7H8), and naphthalene (C10H8), for their potential to form HOMs upon reaction with hydroxyl radicals (OH). We performed flow tube experiments with all three VOCs and focused in detail on benzene HOM formation in the Jülich Plant Atmosphere Chamber (JPAC). In JPAC, we also investigated the response of HOMs to NOx and seed aerosol. Using a nitrate-based chemical ionisation mass spectrometer (CI-APi-TOF), we observed the formation of HOMs in the flow reactor oxidation of benzene from the first OH attack. However, in the oxidation of toluene and naphthalene, which were injected at lower concentrations, multi-generation OH oxidation seemed to impact the HOM composition. We tested this in more detail for the benzene system in the JPAC, which allowed for studying longer residence times. The results showed that the apparent molar benzene HOM yield under our experimental conditions varied from 4.1 % to 14.0 %, with a strong dependence on the OH concentration, indicating that the majority of observed HOMs formed through multiple OH-oxidation steps. The composition of the identified HOMs in the mass spectrum also supported this hypothesis. By injecting only phenol into the chamber, we found that phenol oxidation cannot be solely responsible for the observed HOMs in benzene experiments. When NOx was added to the chamber, HOM composition changed and many oxygenated nitrogen-containing products were observed in CI-APi-TOF. Upon seed aerosol injection, the HOM loss rate was higher than predicted by irreversible condensation, suggesting that some undetected oxygenated intermediates also condensed onto seed aerosol, which is in line with the hypothesis that some of the HOMs were formed in multi-generation OH oxidation. Based on our results, we conclude that HOM yield and composition in aromatic systems strongly depend on OH and VOC concentration and more studies are needed to fully understand this effect on the formation of HOMs and, consequently, SOA. We also suggest that the dependence of HOM yield on chamber conditions may explain part of the variability in SOA yields reported in the literature and strongly advise monitoring HOMs in future SOA studies.

A Ketimide-Stabilized Palladium Nanocluster with a Hexagonal Aromatic Pd7 Core.

Herein, we report the synthesis and characterization of the mixed-valent, ketimide-stabilized Pd7 nanosheet, [Pd7(N═CtBu2)6] (1), via reaction of PdCl2(PhCN)2 and Li(N═CtBu2). tBuCN, isobutylene, and isobutane are also formed in the reaction. The presence of these products suggests that Li(N═CtBu2) acts as a reducing agent in the transformation, converting the Pd(II) starting material into the mixed-valent Pd(I)/Pd(0) product. Complex 1 features a hexagonal planar [Pd7]6+ core stabilized by six ketimide ligands, which surround the [Pd7]6+ center in an alternating up/down fashion. In situ NMR spectroscopic studies, as well as density functional theory (DFT) calculations, suggest that 1 is formed via the intermediacy of the bimetallic Pd(II) ketimide complex, [(tBu2C═N)Pd(μ-N,C-N═C(tBu)C(Me)2CH2)Pd(N═CtBu2)] (2). DFT calculations also reveal that 1 is a rare example of an all-metal aromatic nanocluster with hexagonal symmetry, sustaining a net diatropic ring-current of 10.6 nA/T, which is similar to that of benzene (11.8 nA/T) or other well-established transition-metal aromatic systems. Finally, we have found that 1 reacts with Ph3P, cleanly forming the tris-ligated 16-electron Pd(0) phosphine complex, Pd(PPh3)3 (3), suggesting that 1 could be a useful precatalyst for a variety of cross-coupling reactions.

Novel representation of vapour-liquid equilibrium curves for multicomponent systems: design of total reflux distillation columns

McCabe Thiele diagrams were developed as a graphical tool for designing binary distillation columns. In this article, the method to construct McCabe Thiele diagrams for multicomponent systems is presented, illustrating specifically at total reflux for ideal and nonideal systems. Firstly, a variety of examples were used to depict the novel representation of the vapour-liquid equilibrium (VLE) in two-dimensional space (2D) as contours of VLE for the generation of the x–y diagram. Once the contours of VLE are represented in 2D various design scenarios can be investigated using the generated plot. Hence the proposed graphical method retains the authenticity, simplicity and versatility of the binary McCabe Thiele method. Through examples, it is shown that the depiction of the contours of VLE is a powerful visual tool to identify the type of separation (difficult or simple separation), azeotropes and tangent pinch points. Thereafter, the procedure for calculating the number of stages is presented at total reflux for ideal and nonideal ternary systems to determine the minimum number of stages required. Several simulations for an acetone, benzene and chloroform system were generated using Aspen Plus™ to validate the proposed graphical method. Lastly, it was shown that the proposed graphical method correlated more closely to rigorous simulation than traditional methods.

Prediction of Vapour Liquid Equilibria for Binary Azeotropic Systems using Activity Coefficient Models

Distillation operations are inevitable in chemical and petrochemical process industries. Design of distillation equipment requires knowledge of precise vapor-liquid equilibrium data. Due to the complexity and expenses incurred to obtain the VLE data experimentally for those systems for which the data are not available, solution thermodynamics and phase equilibria serve as an important tool in theoretical VLE prediction. In the current investigation five binary azeotropes namely Acetone-water, Acetone-methanol, Ethanol-water, Ethanol-benzene, and Methanol-water are taken for study. The theoretical prediction of VLE for these systems were computed using activity coefficient models namely NRTL, UNIQUAC, UNIFAC and modified form of Florry - Huggins equations (SRS and TCRS). The parameters for the five systems of four models viz. NRTL, UNIQUAC, SRS and TCRS were computed using Newton Raphson technique. UNIFAC model was adopted using Analytical solution of group contribution (ASOG) method. The performance of these models are tested using thermodynamic consistency test and validation from experimental VLE from literature. It was seen that the Acetone - Water system follows TCRS model, Acetone - Methanol and Ethanol - Water and Methanol - Water systems follow UNIFAC model, whereas SRS model suits for the Ethanol - Benzene system with highest accuracies.

Evaluation of ionic liquid separation ability for the benzene–methanol mixture by extractive distillation

AbstractBACKGROUNDBenzene–methanol azeotrope can be formed at atmospheric pressure. Extractive distillation is widely used in the separation of azeotrope. The key factor for extractive distillation is the selection of entrainer. The minimal total annual cost of extractive distillation process can be used as objective function to evaluate the separation performance of ionic liquid entrainer. Intermolecular interaction energy can be used to analyze separation mechanisms.RESULTAn Aspen Plus software database belonging to the three ionic liquids 1‐hexyl‐3‐methylimidazolium acetate, 1‐octyl‐3‐methylimidazolium acetate and 1‐decyl‐3‐methylimidazolium acetate was established. The minimal total annual costs of three extractive distillation processes for the separation of benzene–methanol mixture with different ionic liquids were obtained by sequential iterative method. The feed rate of entrainer was also obtained under the optimized conditions. Among the three extractive distillation processes with different ionic liquid, the total annual cost and the entrainer feed rate of the extractive distillation process with 1‐hexyl‐3‐methylimidazolium acetate as entrainer are the smallest. The intermolecular interaction energies in the ternary system of benzene–methanol–ionic liquid were obtained using the Gaussian 09 software package based on the density functional theory. The separation mechanisms and the extractive distillation process of benzene–methanol azeotrope with ionic liquid as entrainer was interpreted by the intermolecular interaction energy.CONCLUSIONThe results show that the separation ability of 1‐hexyl‐3‐methylimidazolium acetate is higher than that of 1‐octyl‐3‐methylimidazolium acetate or 1‐decyl‐3‐methylimidazolium acetate. Intermolecular interaction energy analysis can be used in the screening and design of ionic liquid entrainer. © 2019 Society of Chemical Industry

Comparative thermo-acoustic study of ternary mixture of polar and nonpolar solvents with benzene and ethanol system

The study of liquid mixtures containing polar or nonpolar components finds wide application in industrial and technological processes. The ultrasonic velocity (u) and density (ρ) of the ternary mixtures 1,2 propane-di-ol (polar) + ethanol + benzene (system I) and n-hexane (nonpolar) + ethanol + benzene (system II) as well as of pure components have been measured at 303 K temperature and at 2 MHz frequency. The ultrasonic velocity is measured using ultrasonic interferometry technique, and density is measured using relative density bottle. From these measured data, the excess acoustic parameters: excess ultrasonic velocity (uE), excess density (ρE), excess adiabatic compressibility (βE), excess intermolecular free length ( $$L_{\text{f}}^{\text{E}}$$ ), excess molar volume ( $$V_{\text{m}}^{\text{E}}$$ ) and excess acoustic impedance (ZE), have been calculated using standard relations. The variations in sign and values of excess acoustic parameters of the two systems help us to know the interaction and structural arrangement of the liquid mixture. The values of uE and ZE for system I show that the interaction changes from strong to weak interaction with increasing concentration and for system II it has dispersive-type interaction. There is an opposite trend in the values of ρE, βE, L f E and V m E for systems I and II. System I has smaller molar volume difference compared to system II, but relatively stronger Hp–π interaction gives it a compact structure. However, system II is more compressible due to dispersive-type interaction. Our work helps to understand the effect of the molecular interaction on behavior of liquid mixture of polar and nonpolar solvents in π-system clearly and concisely.

Study of the curing kinetics of melamine/phthalonitrile resin system

The exploration of curing process is important for the application of phthalonitrile resins in advanced materials. In this study, the curing behaviors of 1,3-bis (3,4-dicyanophenoxy) benzene (3BOCN) and melamine (MI) system was studied by differential scanning calorimetry (DSC) at different heating rates. An autocatalytic model could describe the curing reaction of 3BOCN-MI. The curing parameters including apparent activation energy, reaction orders and pre-exponential factor were calculated. The average activation energies for the three different proportions of 3BOCN-MI (8:1, 8:2, 8:3) system were 93, 98 and 96 kJ/mol, respectively. Besides, the predicted models for the reaction of 3BOCN-MI curing fitted well with the experimental data.

Batch experiments to investigate the effect of colloidal silica on benzene adsorption

Benzene is one of the most harmful compounds in groundwater. In the groundwater environment, adsorption plays a major role in benzene attenuation. In this study, laboratory experiments were conducted using jars to systematically investigate the effect of benzene adsorption under static conditions. Experiments were conducted using colloidal silica, which is representative of colloids in groundwater. In the single benzene system, more benzene was adsorbed at high than low pH because of the reduction in available H+ to compete with benzene for adsorption with increased pH. In addition, more benzene was adsorbed at high than low ionic strengths (ISs), because the presence of metal cations neutralized more negative charges and weakened the electrostatic interaction between benzene and the media. In the benzene-colloidal silica system, the presence of colloidal silica accelerated benzene adsorption, because colloidal silica can attach to the surface of the porous media and act as additional sites for adsorption while also enhancing the adsorption capacity of the C–H bonds. As the pH increased, the particle size of the colloidal silica also increased, which increased the colloidal silica adsorption capacity of benzene. As ISs increased, the colloidal silica became more unstable, and colloidal silica could easily attach to the surface of the porous media, enabling more benzene to be adsorbed. However, in the presence of colloidal silica, the effects of pH and ISs on benzene adsorption are not obvious and colloidal silica plays a leading role in benzene adsorption. Colloidal silica promotes benzene adsorption, primarily because it provides sites for adsorption and has a higher affinity for benzene than the surfaces of the porous media. This allows the porous media to rapidly adsorb benzene until reaching the saturation point, which has a much stronger effect on benzene adsorption than hydro-chemical conditions.

Kinetic Studies on the Oxoiron(IV) Complex with Tetradentate Aminopyridine Ligand PDP*: Restoration of Catalytic Activity by Reduction with H2O2

Oxoiron(IV) is a common catalytic byproduct observed in the oxidation of alkenes by the combination of H2O2 and nonheme iron catalysts including complex 1, FeIIPDP* (where PDP* = bis(3,5-dimethyl-4-methoxypyridyl-2-methyl)-(R,R)-2,2'-bipyrrolidine). The oxoiron(IV) species have been proposed to arise by O-O homolysis of the peroxyiron(III) or acylperoxyiron(III) intermediates formed during the presumed FeIII-FeV catalytic cycle and have generally been regarded as off-pathway. We generated complex 1IV═O (λmax = 730 nm, ε = 350 M-1 cm-1) directly from 1 and an oxygen atom donor IBXi-Pr (isopropyl 2-iodoxybenzoate) in acetonitrile in the temperature range from -35 to +25 °C under stopped-flow conditions. Species 1IV═O is metastable (half-life of 2.0 min at +25 °C), and its decay is accelerated in the presence of organic substrates such as thioanisole, alkenes, benzene, and cyclohexane. The reaction with cyclohexane-d12 is significantly slower (KIE = 4.9 ± 0.4), suggesting that a hydrogen atom transfer to 1IV═O is the rate limiting step. With benzene-d6, no significant isotope effect is observed (KIE = 1.0 ± 0.2), but UV-vis spectra show the concomitant formation of an intense 580 nm band likely due to the Fe(III)-phenolate chromophore, suggesting an electrophilic attack of 1IV═O on the aromatic system of benzene. Treatment of 1IV═O with H2O2 resulted in rapid decay of its 730 nm visible band (k = 102.6 ± 4.6 M-1 s-1 at -20 °C), most likely occurring by a hydrogen atom transfer from H2O2. In the presence of excess H2O2, the oxoiron(IV) is transformed into peroxyiron(III), as seen from the formation of a characteristic 550 nm visible band and geff = 2.22, 2.16, and 1.96 electron paramagnetic resonance (EPR) spectroscopy signals. Reductively formed 1III-OOH was able to re-enter the catalytic cycle of alkene epoxidation by H2O2, albeit with lower yields versus those of oxidatively formed (i.e., 1 + H2O2) peroxyiron(III) owing to a loss of ca. 40% active iron. As such, the oxoiron(IV) species can be reintroduced to the catalytic cycle with extra H2O2, acting as an iron reservoir. Alternatively, peroxycarboxylic acids, which have a stronger O-H bond dissociation energy, do not reduce 1IV═O, ensuring that more oxidant is productively employed in substrate oxidation. While this reaction with H2O2 may occur for other nonheme oxoiron(IV) complexes, the only previously reported examples are 3IV═O and 4IV═O, which are reduced by hydrogen peroxide 130- and 2900-fold more slowy, respectively (as in Angew. Chemie - Int. Ed. 2012 , 51 ( 22 ), 5376 - 5380 , DOI: 10.1002/anie.201200901 ).

A Density Functional Theory Study of an Exciplex II: Benzene and Tricyanobenzene

The exciplex of benzene–tricyanobenzene was theoretically investigated at the levels of density functional theory (DFT) and its time‐dependent variation within Tamm–Dancoff approximation (TDA‐DFT) using ωB97X functional and 6–311++G(d,p) basis set. Unlike the benzene and pyridine system studied previously, the charge transfer (CT) character from benzene, the electron donor to tricyanobenzene, the electron acceptor, is observed to be significant in a few low‐lying singlet excited states. Via the crossing and mixing between the states of the same symmetry, however, we also observe the mixed characters between the CT and local excitation (LE) as the intermolecular distance decreases. In the comparison to the benzene–pyridine complex, the enriched CT characters in the low‐lying singlet states stem from the significant energy offsets between the frontier molecular orbitals of benzene and tricyanobenzene, which suppresses their molecular orbital interactions and hence their delocalization.

Accelerating GW-Based Energy Level Alignment Calculations for Molecule-Metal Interfaces Using a Substrate Screening Approach.

The physics of electronic energy level alignment at interfaces formed between molecules and metals can in general be accurately captured by the ab initio GW approach. However, the computational cost of such GW calculations for typical interfaces is significant, given their large system size and chemical complexity. In the past, approximate self-energy corrections, such as those constructed from image-charge models together with gas-phase molecular level corrections, have been used to compute level alignment with good accuracy. However, these approaches often neglect dynamical effects of the polarizability and require the definition of an image plane. In this work, we propose a new approximation to enable more efficient GW-quality calculations of interfaces, where we greatly simplify the calculation of the noninteracting polarizability, a primary bottleneck for large heterogeneous systems. This is achieved by first computing the noninteracting polarizability of each individual component of the interface, e.g., the molecule and the metal, without the use of large supercells, and then using folding and spatial truncation techniques to efficiently combine these quantities. Overall this approach significantly reduces the computational cost for conventional GW calculations of level alignment without sacrificing the accuracy. Moreover, this approach captures both dynamical and nonlocal polarization effects without the need to invoke a classical image-charge expression or to define an image plane. We demonstrate our approach by considering a model system of benzene at relatively low coverage on the aluminum (111) surface. Although developed for such interfaces, the method can be readily extended to other heterogeneous interfaces.

A unified model for the drying of glassy polymer coatings

In this work, a unified model has been developed for the drying of the glassy polymeric coatings by studying the solvent evaporation from the poly(methyl methacrylate)/ethyl benzene system as a one dimensional numerical moving boundary experiment with simultaneous heat and mass transfer. The developed model is based on sound non equilibrium thermodynamics principles by considering visco-elastic contribution to diffusion at the late stage of drying. Moreover, sol-gel transition is considered to explain the high solvent concentration far away from the gas-liquid interface (drying surface) at the end of the drying experiment. The Galerkin finite element method is used to solve the model equations. The model predictions for the drying rate and solvent concentration profiles are found to be in satisfactory agreement with the available experimental data. This work can be implemented to design and optimize industrial processes.