Surface Interaction Energy Research Articles

Revisiting the Most Stable Structures of the Benzene Dimer.

The benzene dimer (BD) is an archetypal model of π∙∙∙π and C-H∙∙∙π noncovalent interactions as they occur in its cofacial and perpendicular arrangements, respectively. The enthalpic stabilization of the related BD structures has been debated for a long time and is revisited here. The revisit is based on results of computations that apply the coupled-cluster theory with singles, doubles and perturbative triples [CCSD(T)] together with large basis sets and extrapolate results to the complete basis set (CBS) limit in order to accurately characterize the three most important stationary points of the intermolecular interaction energy (ΔE) surface of the BD, which correspond to the tilted T-shaped (TT), fully symmetric T-shaped (FT) and slipped-parallel (SP) structures. In the optimal geometries obtained by searching extensive sets of the CCSD(T)/CBS ΔE data of the TT, FT and SP arrangements, the resulting ΔE values were -11.84, -11.34 and -11.21 kJ/mol, respectively. The intrinsic strength of the intermolecular bonding in these configurations was evaluated by analyzing the distance dependence of the CCSD(T)/CBS ΔE data over wide ranges of intermonomer separations. In this way, regions of the relative distances that favor BD structures with either π∙∙∙π or C-H∙∙∙π interactions were found and discussed in a broader context.

Mechanistic Analysis and Process Simulation of Ethyl Acetate-Ethanol Separation by Complex Solvent Extractive Distillation.

Developing high-performance solvents for extraction and optimizing process technologies is crucial for efficient extractive distillation (ED) separation of azeotrope mixtures. In this paper, computer-aided screening was used to study the ED of azeotrope mixtures in ethyl acetate and ethanol systems using organic solvent dimethyl sulfoxide (DMSO) and ionic liquid (IL) ([EMIM][Ac]). The structural relationship between the ILs and the azeotrope mixture was analyzed by σ-profile, molecular surface electrostatic potential, interaction energy, and separation gradient. Subsequently, process simulation was carried out using Aspen Plus software and global optimization was performed with genetic algorithm, which found that both traditional organic solvents and ILs have good separation effects. But considering the high volatility of organic solvents and low saturation vapor pressure of ILs, it is considered to combine them to further explore the cost and carbon emission advantages in extractive distillation separation. Compared with pure organic solvent and pure ILs separation processes, the TAC of the process using an IL-based mixed solvent process decreased by 5.11 and 21.98%, respectively. The carbon emissions of the mixed extractant process were slightly higher than those of the pure organic solvent process, but the addition of ILs made very little volatilization of organic solvents, saving a charge for extractant use. By improving the process, waste heat is effectively recovered, which can save most of the utility engineering costs, and compared with the previous process, the total alkali consumption and carbon dioxide emissions are reduced by 9.43 and 27.17%, respectively. This exploration provides a theoretical reference for the development application and industrial research of ED processes using IL-based mixed solvents.

Origins of the unphysical noncovalent interaction energy curves obtained with the 2011 and 2012 Minnesota density functionals.

With the noncovalent interaction energy curves of the methane dimer [(CH4)2], we have clarified two different origins of the unphysical noncovalent interaction energy curves obtained with the Minnesota density functionals of M11-L, MN12-L, and MN12-SX. For the M11-L functional, the unphysical inflection point on the (CH4)2 interaction energy curve originates from the inclusion of the long-range exchange. As to the MN12-L and MN12-SX functionals, the lack of smoothness restraints results in unphysical inflection points on the corresponding (CH4)2 interaction energy curves. As a result, exchange functionals are as important as dispersion corrections for density functionals to map noncovalent interaction energy surfaces reasonably. Moreover, very highly parameterized functionals with smoothness restraints are suggested for investigating noncovalent interaction energy surfaces.

Investigating Hydrogen Bonding in Quinoxaline-Based Thermally Activated Delayed Fluorescent Materials.

In recent years, hydrogen bonding (H bonding) as an intramolecular locking strategy has been proposed to enhance photoluminescence, color purity, and photostability in thermally activated delayed fluorescence (TADF) materials. Rigidification as a design strategy is particularly relevant when using electron-deficient N-heterocycles as electron acceptors, because these materials often suffer from poor performance as orange to near-infrared emitters as a result of the energy gap law. To critically evaluate the presence of H bonding in such materials, two TADF-active donor-acceptor dyads, ACR-DQ and ACR-PQ, were synthesized. Despite their potential sites for intramolecular H bonding and emissions spanning yellow to deep red, computational analyses (including frequency, natural bond orbital, non-covalent interaction, and potential energy surface assessments) and crystal structure examinations collectively suggest the absence of H bonding in these materials. Our results indicate that invoking intramolecular H bonding should be done with caution in the design of rigidified TADF materials.

Phenolics from Polygonatum cyrtonema Hua extracted using natural deep eutectic solvents combined with auxiliary techniques: Composition, bioactivity, and mechanistic elucidation

This study investigated the natural extraction of polyphenolic compounds from Polygonatum cyrtonema Hua (P. cyrtonema). Employing the combination of natural deep eutectic solvents (NADESs) and auxiliary extraction techniques, we mainly focused on yield, total phenolics, total flavonoids, antioxidant capacity, and enzyme inhibition efficiency. Compared to hot reflux extraction (HRE), the NADES extract using a 1:2 ratio of choline chloride-lactic acid (ChCl-Lac) significantly increased the total phenolic content (TPC), total flavonoid content (TFC), and α-glucosidase inhibition (p < 0.05). The HPLC-MS-MS identified the five most abundant phenolic compounds. Quantitative analysis showed that these compounds had the highest leaching rates in the ultrasonic-assisted extraction (UAE) combined with lactic acid-based NADES system, followed by microwave-assisted extraction (MAE), requiring less than 4 min. Notably, rutin exhibited the highest extraction rate of 281.1 μg/g in the UAE-ChCl-Lac system, 9.82 times higher than conventional methods. The extraction mechanism was elucidated from the perspectives of surface charge density distribution and interaction energy. Therefore, ultrasound or microwave-assisted NADES extraction aligns with sustainable development principles, offering a green approach to enrich polyphenolic compounds in P. cyrtonema.

Fracture behavior of composite piezoelectric intelligent structures formed by pasting MFC based on serial multi-scale method

The composite piezoelectric intelligent structures formed by combining piezoelectric materials with composite materials can achieve state perception and deformation control of the structure. Based on the molecular dynamics method, the continuum finite element method and the cohesive force model, the serial multi-scale research on the bonded composite piezoelectric intelligent structure was carried out from the micro, meso and macro scales. Molecular models of adhesive, macro fiber composite (MFC) surface and composite surface were established. The effects of temperature and pressure on the surface interaction energy of adhesive/MFC and adhesive/composite materials were analyzed. The traction-separation (T-S) relationship of cohesive region was obtained by virtual stretching method. Combined with the microscopic observation of the mesoscopic adhesive layer, the representative volume element (RVE) model of the mesoscopic adhesive layer considering the bubble defect was established, and the cohesive relationship curve of the adhesive layer was obtained. A double cantilever beam (DCB) macro finite element model was established to simulate the crack propagation behavior of the adhesive layer, and compared with the experimental results.

Confined and spontaneously transformed oxidation structures due to the intrinsic heterogeneous surface morphology of C3N monolayer.

Identifying the oxidation structure of two-dimensional interfaces is crucial to improve surface chemistry and electronic properties. Beyond graphene with only phenyl rings, a novel carbon-nitrogen material, C3N, presents an intrinsic heterogeneous surface morphology where each phenyl ring is encircled by six nitrogen atoms, yet its atomistic oxidation structure remains unclear. Here, combining a series of density functional theory calculations and abinitio molecular dynamics simulations, we demonstrate that thermodynamically favorable oxidation loci are confined to the phenyl ring, and kinetic transformations of oxidation structures are feasible along the phenyl ring, whereas those toward nitrogen atoms are proven to be extremely difficult. These results are attributed to the lower barrier of oxygen atom migration along the phenyl ring, while the significantly high barriers toward nitrogen atoms are due to the heterogeneous potential energy surface for oxygen-C3N interaction. This work highlights the significance of surface morphology on the characteristics of oxidation structure, offering insights into tunable electronic properties via confined interfacial oxidation.

Unexpectedly High Propylene/Propane Separation Performance of Asymmetric Mixed-Matrix Membranes through Additive-Assisted In Situ ZIF-8 Filler Formation: Experimental and Computational Studies.

Zeolitic-imidazolate framework-8 (ZIF-8), composed of a zinc center tetrahedrally coordinated with 2-methylimidazolate linkers, has garnered extensive attention as a selective filler for propylene-selective mixed-matrix membranes (MMMs). Recently, we reported an innovative and scalable MMM fabrication approach, termed "phase-inversion in sync with in situ MOF formation" (PIMOF), aimed at addressing the prevailing challenges in MMM processing. In this study, we intend to investigate the effect of additives, specifically sodium formate and 1,4-butanediol, on the modification of ZIF-8 filler formation within the polymer matrix in order to further improve the separation performance of the asymmetric MMMs prepared by the PIMOF. Remarkably, MMMs prepared with sodium formate as an additive in the coagulation bath exhibited an unprecedented C3H6/C3H8 separation factor of 222.5 ± 1.8 with a C3H6 permeance of 10.1 ± 0.3 GPU, surpassing that of MMMs prepared without additives (a C3 separation factor of 57.7 ± 11.2 with a C3 permeance of 22.5 ± 4.5 GPU). Our computational work complements the experimental investigation by studying the effect of ZIF-8 nanoparticle size on the specific surface interaction energy and apertures of ZIF-8. Calculations indicate that by having smaller ZIF-8 nanoparticles, stronger interactions are present with the polymer affecting the aperture of ZIF-8 nanoparticles. This reduction in aperture size is expected to improve selectivity toward propylene by reducing the permeability of propylene. These results represent a significant advancement, surpassing the performance of all previously reported propylene-selective MMMs and most high-quality polycrystalline ZIF-8 membranes. The notably enhanced separation performance primarily arises from the formation of exceedingly small ZIF-8-like particles with an amorphous or poorly crystalline structure, corroborated by our computational work.

Construction of intermolecular σ-hole interactions in rare earth metallocene complexes using a 2,3,4,5-tetraiodopyrrolyl anion.

The generation of noncovalent intermolecular interactions represents a powerful method to control molecular vibrations and rotations. Combining these with the axial ligand field enforced by the metallocene ligand scaffold provides a dual-pronged approach in controlling the magnetic-relaxation pathways for dysprosium-based single-molecule magnets (SMMs). Here, we present the first implementation of 2,3,4,5-tetraiodopyrrole (TIPH) in its anionic form [TIP]- as a ligand in three isostructural rare-earth metal complexes Cp*2RE(TIP) (1-RE, RE = Y, Gd, and Dy; Cp* = pentamethylcylopentadienyl), where the TIP ligand binds through the nitrogen and one iodine atom κ2(N,I) to the metal centre. The shallow potential energy surface of the intermolecular σ-hole interaction yields distortions of the interatomic distances at elevated temperatures which were investigated by variable-temperature SCXRD. 1-RE constitute the first crystallographically characterized molecules containing TIP as a ligand for any metal ion, and 1-Dy is the first SMM that employs the TIP ligand. The structural dependence on temperature allowed the mechanism of magnetic relaxation to be explored through ab initio calculations at different temperatures. The electronic influence of the coordinated iodine substituent was probed via magnetometry and cw-EPR spectroscopy on 1-Gd. To further scrutinize the impact of the iodine substituents on the physical properties, a second set of new complexes Cp*2RE(DMP) (2-RE, RE = Y, and Dy) where DMP = 2,5-dimethylpyrrolyl were synthesized. Here, the DMP ligand binds similarly to the TIP ligand and represents an all-hydrocarbon analogue to 1-RE. 2-Dy constitutes the first SMM bearing a DMP ligand.

Steviol glycosides improve the textural properties of whey protein gel

Steviol glycosides (SGs) have been used as non-nutritive sweeteners widely in various food matrixes. In this experiment, SGs including natural SGs and a synthetic glucosyl steviol glycoside were found to be capable to modulate heat-induced gelation of whey protein isolate (WPI), improved the gel properties such as rheological, water holding capacity, textural, thermal stability and microstructural properties. Within the SGs concentration up to 1.0 wt%, enhancement on the textural properties of WPI was concentration-dependent. With 1 wt% of assayed SGs, the storage modulus, loss modulus, gel strength of SG-WPI gel were up to 11.2-fold, 4.6-fold, 5.2-fold of that of the gels free of SGs, respectively. The frequency sweep indicated that the SGs could also attenuate the frequency dependence of WPI gel in a concentration-dependent manner. The ability of the SGs to improve the gelation properties of WPI followed the same sequence of their surface activity and interaction energy: Rubusoside ∼ Monoglucosyl rebaudioside A > Stevioside > Rebaudioside A.

In-depth Hirschfeld Surface Analysis, Interaction Energy, Molecular Docking, and DFT Investigations of Electronic Properties of 2,4-dimethyl-1-nitrobenzene

Quantum-chemical calculations, molecular docking, and Hirshfeld surface analysis of a structure of 2,4-dimethyl-1-nitrobenzene constitute the main aspects of this work. The crystal structure of the title compound which is liquid at room temperature, was obtained by in situ cryo crystallization The crystal packing is stabilized by C5–H5…O2 and C7–H7C…N1 intermolecular hydrogen bonds. The analysis of the obtained results of the density functional theory calculations is in good agreement with the experimental data. The analysis of global chemical reactivity descriptors shows that the compound exhibits more stability and less reactivity at high polar media. Hirshfeld surface and 2D-fingerprint plots analysis shows that the H…H, O…H/H…O, C…C, and C…H/H…C contacts are the significant contributors stabilizing the crystal structure of 2,4-dimethyl-1-nitrobenzene. The RDG-NCI analysis of the molecule was performed to determine the non-covalent interactions present within the molecule. In addition, the compound under investigation presents a biological activity when it is docked into the protein (PDB ID: 4Y0S) with the binding energy system of -6.6 kcal/mol.

Particle growth across the scales: A combination of ab initio, molecular dynamics, and kinetic Monte Carlo simulations for Fe2Al5 in liquid Zn

We study the growth of Fe2Al5 particles in liquid Zn with a multi-scale approach from ab initio molecular statics and dynamics to kinetic Monte Carlo (kMC) simulations. This includes computation of the transition rates, i.e. adsorption rates from diffusion of elements in liquid Zn and desorption rates from surface desorption energies and interaction energies of atoms at the surface. Adsorption and desorption rates together with the correct crystal structure are the main input for the kMC simulations. With systematic kMC simulations, we then map out the growth rates of Fe2Al5 at different temperatures and varying chemical compositions. Altogether, this constitutes an approach that is also applicable to other studies focusing e.g. on deposition processes or dissolution of particles.

Crystal structure, Hirshfeld surface analysis, inter-action energy and energy framework calculations, as well as density functional theory (DFT) com-putation, of methyl 2-oxo-1-(prop-2-yn-yl)-1,2-di-hydro-quinoline-4-carboxyl-ate.

In the title mol-ecule, C14H11NO3, the di-hydro-quinoline core deviates slightly from planarity, indicated by the dihedral angle of 1.07 (3)° between the two six-membered rings. In the crystal, layers of mol-ecules almost parallel to the bc plane are formed by C-H⋯O hydro-gen bonds. These are joined by π-π stacking inter-actions. A Hirshfeld surface analysis revealed that the most important contributions to the crystal packing are from H⋯H (36.0%), H⋯C/C⋯H (28.9%) and H⋯O/O⋯H (23.5%) inter-actions. The evaluation of the electrostatic, dispersion and total energy frameworks indicates that the stabilization is dominated by the dispersion energy contribution. Moreover, the mol-ecular structure optimized by density functional theory (DFT) at the B3LYP/6-311G(d,p) level is com-pared with the experimentally determined mol-ecular structure in the solid state. The HOMO-LUMO behaviour was elucidated to determine the energy gap.

Isomorphic relationship between three solvates of a ferrocenyl-based chromenopyrimidine

Solvates of 4-((3-ferrocenylphenyl)amino)-5-(2-fluorophenyl)-8,8-dimethyl-5,7,8,9-tetrahydro-6H-chromeno[2,3-d]pyrimidin-6-one (I), a promising antiproliferative agent towards human breast cancer (MCF-7) cells, were formed from their respective acetone, DMSO‑d6, and DMF solutions. Isomorphic relationship exists between the solvates of I since all compounds crystallize in a P21/n space group with four molecular entities in their respective unit cells, with slight differences in their respective unit cell parameters. IR spectroscopy was used to distinguish the three solvates by monitoring the NH vibration frequency since they all have intermolecular NH…Osolvent hydrogen bonding patterns in the solid state. The solvent molecule's Hirshfeld surface helps distinguish the solvates based on the contribution of reciprocal H…O contacts. Molecular pairwise interaction energy calculations were done to determine the associated energies between solvent-I molecular pairs that are linked by the intermolecular NH…Osolvent hydrogen bond. Correlations between the geometric parameters of the NH…Osolvent hydrogen bond, NH vibration frequency, the contribution of reciprocal H…O contacts toward the solvent's Hirshfeld surface and pairwise interaction energies of the three solvates, are discussed in this work.

Potential energy surfaces of antiparallel water-water interactions

Antiparallel water-water interaction is a significant interaction between two water molecules and plays an important role in liquid water. The potential energy surface of antiparallel water-water interaction was calculated at accurate CCSD(T)/CBS level of theory by systematic changes of the torsion angle THOHO, parallel displacement r, normal distance R, and water-water dihedral angle Pa/Pb. The results show that the most stable geometry of antiparallel water-water interaction has an interaction energy of −4.22 kcal/mol and THOHO = 140°. A significant portion of the antiparallel interactions have interaction energies more negative than −2.0 kcal/mol. The angle α of the most stable geometries of antiparallel water-water interactions is in the range 110°–120°. Comparison with classical hydrogen bonds in water dimers shows that hydrogen bonds with values of angle α < 140° have interaction energies up to −3.2 kcal/mol, while a significant number of antiparallel water-water interactions is stronger than it. The antiparallel geometry is a low barrier transition state between two hydrogen bonded minima with changed acceptor–donor roles of two water molecules.

Optical activity and linear electrooptic response in the paraelectric subphase of an achiral ferroelectric nematic compound

ABSTRACTPolarizing optical microscopy and electro optics are used to study a compound with constituent non-chiral molecules, DIO, known to exhibit three nematic phases, namely N, Nx and ferronematic NF. N is found to be a conventional nematic but shows two additional unusual features: the presence of optically active domains and a linear electro optic response to the applied signal. The optical activity is explained by a segregation of the stable helical conformers of the opposite sense; these preferring to form domains with an optical rotation of ±4°/μm. This is the first example of helical segregation observed in non-chiral molecules in the high temperature nematic phase. Unlike the ordinary nematic liquid crystalline material, this compound shows a linear electro optical response to the applied electric field, thereby confirming the polar nature of this phase. NF is the ferroelectric nematic as reported previously. The strong polar azimuthal surface interaction energy in the NF phase stabilises a homogeneous structure in planar-aligned cells that are rubbed parallel and gives a twisted structure in cells rubbed antiparallel.

Revealing mechanism of non-Arrhenius viscosity change in metal melts based on Wulff cluster model

In some metal melts, like Pb and Al, viscosity as a function of temperature does not obey Arrhenius law in some temperature range, so called non-Arrhenius viscosity change. In this paper, the Wulff cluster model combined with phonon calculations is used to investigate the relation between the structural characteristic and the non-Arrhenius viscosity change in metallic melts. Although the surface energy of the Wulff clusters in melts does not change significantly with temperature, the Wulff shape changed evidently. For both Pb and Al, one surface of the Wulff shape disappears (Pb(321) and Al(100)) when the non-Arrhenius viscosity change occurs upon heating. The trend of the non-Arrhenius viscosity change is strongly related to the properties of the disappeared surface. The non-Arrhenius viscosity drop corresponds to the disappearance of the surface with the highest interaction energy between surface and free atoms (Pb(321) surface), while the non-Arrhenius viscosity rise corresponds to the disappearance of surface with the lowest interaction energy (Al(100) surface). All evidence indicates that the viscosity anomaly and the change of Wulff shape is closely related. The non-Arrhenius viscosity change in metallic melts is caused by the appearance/disappearance of certain surfaces of clusters, while the interaction strength of these surfaces determines the different features (non-Arrhenius drop/rise) of corresponding viscosity change.

Synthesis, single crystal X-ray structure determination, Hirshfeld surface analysis, interaction energies, and density functional theory calculations of N,N'-(cyclohexane-1,4-dicarbonothioyl)bis(4-methylbenzamide)

The present research offers convenient synthesis, molecular and crystal structures of C2 symmetric N,N'-(cyclohexane-1,4-dicarbonothioyl)bis(4-methylbenzamide). The synthesized bis-amide crystallized in monoclinic crystal system, having space group of P 21/c with a = 17.8669 (14) Å, b = 6.3495 (5) Å, c = 9.6195 (7) Å, β = 101.567 (8)°, Z = 2 and V = 1069.13 (15) Å3. The asymmetric unit contains cyclohexane ring located on an inversion center, one dicarbonothioyl and one methylbenzamide group. In the crystal structure, the N–H···O, C–H···O and C–H···S hydrogen bonds link the molecules, enclosing R21(6), R22(16) and R22(22) ring motifs, into three-dimensional architecture. Hirshfeld surface (HS) analysis revealed the prevailing significance of hydrogen bond contacts. HS analysis suggested prominent contributions for crystal packing encompasses H…H (49.6%), H…C/C…H (18.9%) and H…S/S…H (16.0%). Hydrogen bonding and van der Waals contacts are the dominant interactions in the crystal packing. The respective volume of the crystal voids and the percentage of free spaces in the unit cell is calculated as 117.87 Å3 and 11.02% indicating the absence of any large cavity within the crystal and the associated stability of the crystal. Evaluation of the electrostatic, dispersion and total energy frameworks revealed that stabilization is dominated by dispersion energy contribution. Moreover, optimized molecular structure, using density functional theory at B3LYP/6-311G(d,p) level, were compared with the experimentally determined ones. HOMO–LUMO energy gap was determined, frequencies and molecular electrostatic potential surface were calculated at the B3LYP/6–311G level to predict sites for electrophilic and nucleophilic attacks. The significant charge polarity, half molecule spread of HOMO and LUMO impart bis-amide nucleophilic as well as electrophilic behavior with relative potency depending upon the nature of the attacking molecule.

Microstructural transformations of swelling clay minerals

An original model of microstructural transformations during clay swelling is considered, a thermodynamic and physical-mechanical description of the properties of clays during the process of swelling in vapors and aqueous solutions is given. The model proposed to explain these properties is based on the concept of mutual displacement of clay particles in clay rock aggregates during swelling with the formation of new pores between clay particles forming crystallites and aggregates. The model is based on the mechanism of utilization of the excess surface energy of clay particles during hydration, taking into account the influence of certain environmental parameters, for example, the concentration of the solution, through a change in the mutual orientation of clay particles, mainly due to rotations or shifts relative to each other, with the formation of an area available for further wetting free surface. In the thermodynamic description, such a process will manifest itself in a change in the surface interaction energy on the wetted areas of the particles when moving during mutual shifts and rotations. At the same time, one of the most important parameters of clay rock, microporosity, also changes. In this work, this phenomenon was experimentally studied using the methods of static moisture capacity and Mössbauer (NGR) spectroscopy. The proposed model makes it possible to explain the features of the clay hydration process and to compare the observed experimental data with the theoretical description of the clay swelling process.

Review of Colloid (Nano‐ and Micro‐Particle) Transport and Surface Interaction in Groundwater. William P. Johnson and Eddy F. Pazmino. The Groundwater Project. 111 pp. ISBN: 978‐1‐77470‐070‐9. DOI: https://doi.org/10.21083/978‐1‐77470‐070‐9

Review of <i>Colloid (Nano‐ and Micro‐Particle) Transport and Surface Interaction in Groundwater</i>. William P. Johnson and Eddy F. Pazmino. The Groundwater Project. 111 pp. ISBN: 978‐1‐77470‐070‐9. DOI: https://doi.org/10.21083/978‐1‐77470‐070‐9