Second-order Energy Research Articles

Evaluation of hydrogen bonds formation in the selected rare sugars based on 6-31G* and 6-311 + + G(d,p) basis sets.

Rare sugars are monosaccharides with tremendous potential for applications in pharmaceutical, cosmetics, nutraceutical, and flavors industries. The four rare sugars, including gulose, allose, altrose, and talose, are stereoisomers that are different in the hydroxyl group orientation (axial or equatorial) on the C2-4atoms. The basis sets effect in evaluation of the possibility intramolecular hydrogen bonding (H-bonds) in the selected rare sugars was studied from 6-31G* to 6-311 ++ G(d,p) basis sets using DFT, AIM, and NBO methods. The results show that the selected rare sugars are more stable at 6-311 ++ G(d,p) basis sets compared to 6-31G* because their electronic energies were reduced between 158 and 164 (kcal.mol-1). The overall effect of basis set enhancement is to decrease H-bond energies in the range of 1.25 to 2.51 (kcal.mol-1) and stabilization energies between 2 and 5 (kcal.mol-1) in the selected rare sugars at the DFT level of theory. The intramolecular H-bond distances, H-bond energies obtained from the AIM analysis, and alsothe second-order stabilization energies obtained from the NBO analysis were fluctuated largely depending on the basis set. In summary, it was found that the use of 6-311 ++ G(d,p) basis set to be more efficient results in rare sugars geometry than the 6-31G* basis set.

Investigation of heat transfer in wavy and dual wavy micro-channel heat sink using alumina nanoparticles

Thermal management is crucial for the proper functioning of a system whether it is in electronics, process industry, automobile, and renewable devices. Micro-channel heat exchanger has proved to be efficient in heat ejection from renewable systems due to high heat transfer surface to volume ratio. This study focuses on evaluating the cooling performance of straight, wavy, and dual wavy Micro-Channel Heat Exchanger by modelling the heat transfer model in ANSYS Fluent. The incompressible fluid is considered in the laminar regime using alumina-based nanofluids with 1%, 3%, and 6% concentration. The solution is computed by selecting SIMPLE pressure-velocity coupling scheme with second-order momentum and energy discretization. Nusselt number, pressure drop, base temperature, and Thermal Performance Factor (TPF) are used as performance parameters for comparing nanofluids performance at Reynolds number range of 100–900. For straight, wavy, and dual wavy model heat transfer, as well as pressure drop, increased with Reynolds number. It is observed that wavy and dual wavy channels compared to straight channel improved convective heat transfer due to the formation of secondary vortices at the curved section. Dual wavy with wavy base and flat base wall showed highest Nusselt number increase of more than double when compared with straight channel of equal concentration. For 6% nano particles addition in all channels, on average both dual wavy channels showed highest improvement of 8% when compared with 0% concentration channel. Dual wavy channel with a flat base and wavy base reduced the base heater temperature by 10 °C and 9 °C compared to the straight channel. A maximum Thermal Performance Factor of 2.2 is achieved for dual wavy channel with a wavy base configuration with 6% nanoparticles.

Metal Effect Meets Volcano Plots: A DFT Study on Tris(phosphino)borane-Transition Metal Complexes Catalyzed H2 Activation.

Bifunctional transition metal complexes are of particular interest in metal-ligand cooperative activation of small molecules. As a novel type of bifunctional catalyst, Lewis acid transition metal (LA-TM) complexes have attracted increasing interest in hydrogen activation and storage. To advance the catalyst design, herein the metal effect of LA-TM complexes on the hydrogen activation has been systematically studied with a series of tris(phosphino)borane (TPB) complexes with V, Cr, Mn, Fe, Co, and Ni as metal centers. The metal effect not only influences the mechanism of hydrogen activation, but also notably casts a volcano plot for the activity. TPB complexes of V, Cr, Mn, Fe, and Co tend to activate H2 through a stepwise mechanism, while TPB-Ni prefers a synergetic mechanism for H2 activation. More importantly, the metal effect significantly influences the activity of H2 activation and the formation of the LA-H-TM bridging hydride. The trend of changes in the LA-H-TM structures, the second-order perturbation stabilization energies, and the Laplacian bond orders, along with different metals (from V to Ni), are all interestingly constitute volcano plots for the performance of TPB-TM complexes catalyzed H2 activation. TPB-Mn and TPB-Fe are found to be the optimal catalysts among the discussed TPB-TM complexes. The volcano plots disclosed for the metal effects should be informative and instructive for homogeneous and heterogeneous LA-TM catalysts development.

Adsorption of alkali and alkaline earth ions on nanocages using density functional theory

The adsorption of alkali and alkaline earth ions onto the exterior surface of inorganic nanocages X12Y12 (X = B, Al, Ga and Y = N, P, As) was investigated by using the density functional theory (DFT). All of the configurations, including the pristine ions or nanocages, as well as the ion adsorbed nanocage systems, were optimized using B3LYP-D3 functional and DEF2-TZVP basis sets. Comparative single point energy calculations were performed using different functionals viz. B3LYP-D3, M06-2X, ωB97XD and CAM-B3LYP, together with DEF2-TZVP and DEF2-QZVP basis sets. The results of natural bond orbital (NBO), quantum theory of atoms in molecules (QTAIM), and non-covalent interaction (NCI) analyses were compatible with the results of electronic properties. Total density of states (TDOSs), the natural charge, Wiberg bond index (WBI), natural electron configuration, donor–acceptor NBO interactions and second-order perturbation energies are obtained. Strong interaction between the ions and the nanocages is observed and the tendency of the ions to adsorb onto the surfaces of the mentioned X12Y12 nanocages is in the order Be++ > Mg++ > Ca++ > Li+ > Na+ > K+. These nanocages may be potential sensors for these alkali and alkaline earth ions.

Study on desulfurization mechanism of ionic liquid extractant based on Gaussian quantitative calculation

In this paper, five kinds of ionic liquids (ILs) are selected as desulfurization extractants to study the desulfurization mechanism. Based on density functional theory (DFT), B3LYP functional and 6–31++G** basis set, Quantum chemistry calculations were carried out on each substance. And the interaction mechanism between the ionic liquid extractant, benzothiophene (BT), and N-octane (OC) was explored. Through quantitative calculation, the interaction energy between the three is obtained. Natural Bond Orbital theory (NBO) analysis, AIM analysis and RDG analysis are adopted to study the desulfurization mechanism from the second-order perturbation energy of chemical bond orbits, charge migration, hydrogen bonding, and other types of van der Waals forces, etc. The results show that in the interaction force between ILs and BT, electrostatic interaction is the main force, followed by hydrogen bonding, π-π interaction and other types of weak interactions such as van der Waals forces have a certain degree of desulfurization.

Experimental (X-ray, TGA) and computation (NBO, AIM) studies of Iron(II) complex with thiabendazole and 5-aminoisophthalate

In this article, we synthesized the coordination complex: thiabendazole (TBZH) iron 5-aminoisophthalate (AIP), ([(Fe(TBZH)(AIP)(3H2O)]·2.5 H2O), and characterized by the X-ray single crystal diffraction analysis, the result reveals the iron center is six coordinated and formed a slightly distorted octahedron coordinated geometry. In the structure, the Nitrogen of AIP adopts κN coordination mode connecting the metal center and the two carboxylate groups are deprotonized. The TGA manifests there are three weight loss steps and the residue suggest it to be the ferroferric oxide. The Hirshfeld analysis reveals in dnorm-surfac, the O(N)–H···O hydrogen-bonds corresponds to the dark red spots near the hydrogen-bonds acceptor and donor atoms. The presence of patterns of red- and blue triangles on the same region of the shape-index surfaces is a characteristic of π···π stacking. The theoretical calculated the molecular orbitals, it shows that the LUMO orbital, the electron cloud is located at coordinated water molecules (O1, O3) and the free water (O1w). The electron cloud of the HOMO orbitals is mainly sited at the carboxylate groups and the benzene rings of AIP. The bond orders reveal the value of Fe-N1 and Fe-N2 are larger than that of the Fe-N4, Fe-O3, Fe-O2 and Fe-O1. The second-order perturbation energy analysis shown the most of the E(2) stabilization energies of LP(N) → LP*(Fe) is larger than those of the LP(O) → LP*(Fe), indicating the N atom in complex is the main contributor to the coordination. The AIM analysis found the bond critical point (BCP) of the complex, the electron density value ρBCP (from 0.007 to 0.034 a.u.) for the O(C)–H···O hydrogen bonds are all in the suggested interval of 0.002–0.035 a.u. the ρBCP order of Fe-N and Fe-O sequences are ρBCP(Fe-N1) > ρBCP(Fe-N2) > ρBCP(Fe-N4) and ρBCP(Fe-O1) > ρBCP(Fe-O3) > ρBCP(Fe-O2) shown the firm degree of the bond, these are consistent with the bond order. The Laplacian of electron density (∇2ρBCP) are positive and the |v(r)|/g(r) < 1 indicated the O(C)–H···O are mainly closed shell and Fe–O(N) interactions are the intermediate character between the closed shell and the typically covalent interaction.

Structure and hydrogen bonding of mono-protic ionic liquids composed of N-alkylethylenediaminium cations and trifluoromethanesulfonate anion

The stabilities of some of the possible molecular structures, intermolecular hydrogen bonding interactions, and protonation sites of chelating mono-protic ionic liquids composed of N-alkyl (= Hexyl, Octyl, and 2-Ethylhexyl) ethylenediaminium cations with a trifluoromethanesulfonate anion (TFS), forming [HHex][TFS], [HOct][TFS] and [HEtHex][TFS] were studied using DFT calculations with the M06-2X functional and 6-311G(d, p) basis set. The BSSE-corrected interaction energies (∆E0BSSE) for the investigated structures range from − 98.3 to − 108.3 kcal mol−1. NBO and AIM analyses were applied to quantify the relative strengths of the hydrogen bonding interactions and to account for their effect on the stability of various molecular structures. The values of ∆E0BSSE decrease with increasing alkyl chain length and upon introduction of an ethyl branch in the cation. The second-order perturbation energy and electron density indicate that [HAlkyl]1＋[TFS] (protonated at the primary amine, Form A) are more stable than [HAlkyl]2＋[TFS] (protonated at the secondary amine, Form B).

A DFT Study on the Interaction of Doped Carbon Nanotubes with H2S, SO2 and Thiophene

The interactions of simple and Al-, B-, N-, S-, P-, and Si-doped carbon nanotubes with three sulfur-containing molecules (H2S, SO2, and thiophene) were investigated to assess their adsorption potencies and sensor abilities. The DFT method was used to calculate the adsorption energies and natural bond orbitals parameters. In addition, population analyses were performed to calculate the energy gaps and reactivity parameters. The results showed an exothermic interaction of H2S, SO2, and thiophene with simple and doped carbon nanotubes, while the maximum negative adsorption energies belong to Al- and B-containing complexes. Furthermore, evaluation of second-order perturbation energies (obtained from natural bond orbitals calculations) confirmed that the highest energies were related to B- and Al-containing intramolecular interactions. The results revealed the favorability of adsorption of SO2 by nanotubes (B- and Al-doped carbon nanotubes, in particular) compared with the other examined adsorbates.

Investigation on electronic structure, vibrational spectra, NBO analysis, and molecular docking studies of aflatoxins and selected emerging mycotoxins against wild-type androgen receptor

The geometry, frontier molecular orbitals (FMOs), vibrational, NBO analysis, and molecular docking simulations of aflatoxins (B1, B2, M1, M2, G1, G2), zearalenone (ZEA) emodin (EMO), alternariol (AOH), alternariol monoethyl ether (AMME), and tenuazonic acid (TeA) mycotoxins have been extensively theoretically studied and discussed based on quantum density functional theory calculations using Gaussian 16 software package. The theoretical computation for the geometry optimization, NBOs, and the molecular docking interaction was conducted using Density Functional Theory with B3LYP/6-31+G(d,p), NBO program, and AutoDock Vina tools respectively. Charge delocalization patterns and second-order perturbation energies of the most interacting natural bond orbitals (NBOs) of these mycotoxins have also been computed and predicted. Interestingly, among the mycotoxins investigated, aflatoxin G1 is seen to give the strongest stabilization energy while Zearalenone shows the highest tendency to accept electron(s) and emodin, an emerging mycotoxin gave the best binding pose within the androgen receptor pocket with a mean binding affinity of -7.40 kcal/mol.

Cationic effect on properties related to thermal stability and ignition delay for hypergolic ionic liquids

Hypergolic ionic liquids (HILs) are considered as a promising alternative of toxic hydrazine derivatives in the field of liquid bipropellants. The anionic structure plays an important role in determining the hypergolic performance of HILs. Nevertheless, the structure–activity relationship between the cationic structure and ignition properties is still unclear. In this study, the aromaticity, electrostatic potentials (ESPs), natural bond orbital (NBO) analysis, and molecular orbital gap of 25 ionic liquids based on dicyanamide anion were studied to gain more insight into the correlation between cationic structure and hypergolic properties. For the HILs based on the same type of cation with different substituents, better aromaticity leads to better thermal stability of HILs. For the HILs with different types of cations, when the ESPs distribution is relatively concentrated around a certain value, the thermal stability of HILs is relatively higher. The second-order perturbation energy (E(2)) would be responsible for ignition delay (ID) time. The larger the E(2), the more stable the system, and the longer the ID time of HILs. It is also proved for the first time that the energy gap between the HOMO of cations and LUMO of HNO3 could not be used as a method to determine whether this cation-based IL is hypergolic. All these results can be fully justified with experimental data and have important theoretical instructive significance in the design of new high-performance HILs.

Probing structural and electronic properties of divalent metal Mg n+1 and SrMg n (n = 2–12) clusters and their anions

Divalent metal clusters have received great attention due to the interesting size-induced nonmetal-to-metal transition and fascinating properties dependent on cluster size, shape, and doping. In this work, the combination of the CALYPSO code and density functional theory (DFT) optimization is employed to explore the structural properties of neutral and anionic Mg n + 1 and SrMg n (n = 2–12) clusters. The results exhibit that as the atomic number of Mg increases, Sr atoms are more likely to replace Mg atoms located in the skeleton convex cap. By analyzing the binding energy, second-order energy difference and the charge transfer, it can be found the SrMg9 cluster with tower framework presents outstanding stability in a studied size range. Further, bonding characteristic analysis reveals that the stability of SrMg9 can be improved due to the strong s–p interaction among the atomic orbitals of Sr and Mg atoms.

OO-REMP: Approaching Chemical Accuracy with Second-Order Perturbation Theory.

We present a perturbation theory (PT) providing second-order energies that reproduce main group chemistry benchmark sets for reaction energies, barrier heights, and atomization energies with mean absolute deviations below 1 kcal mol-1. The PT is defined as a constrained mixture of the unperturbed Hamiltonians of the Retaining the Excitation degree (RE) and the Møller-Plesset (MP) PTs. The orbitals of the reference wave function, a single unrestricted Slater determinant, are iteratively optimized to minimize the total energy. For all benchmark sets, good and near optimal performance of OO-REMP was observed for an unperturbed Hamiltonian consisting of 25% MP and 75% RE contributions.

Second-order accurate and energy stable numerical scheme for an immiscible binary mixture of nematic liquid crystals and viscous fluids with strong anchoring potentials

We consider in this paper numerical approximations of the immiscible binary mixture of nematic liquid crystals (LCs) and viscous fluids. We develop a second-order time marching scheme by adopting the recently developed stabilized-SAV (scalar auxiliary variable) approach where several critical stabilization terms are added to enhance the stability; thus, large time steps are allowed in computations. The scheme is highly efficient and one only needs to solve several decoupled linear equations with constant coefficients at each time step. The energy stability of the scheme is proved, and various 2D and 3D numerical experiments including the drop deformations and phase separations are then performed to validate the accuracy and energy stability of the proposed scheme.

Modeling the DFT structural and reactivity studies of a pyrimidine -6-carboxylate derivative with reference to its wavefunction-dependent, MD simulations and evaluation for potential antimicrobial activity

Spectroscopic, electronic and chemical properties and molecular docking simulations of ethyl-2-(4-ethoxybenzylidene)-7-methyl-3-oxo-5-(4-benzyloxyphenyl)-2,3-dihydro-5H-[1,3] thiazolo [3,2-a]pyrimidine-6-carboxylate (EMTP) have been extensively studied and discussed on DFT calculations. Using potential energy scans for various rotable bonds to obtain the lowest energy conformer, conformational analysis was achieved. Electronic, chemical, and drug-likeness properties are analyzed. Charge delocalization patterns and second-order perturbation energies of the most interacting natural bond orbitals have also been computed and predicted from wavefunction analysis. To understand the interaction between receptor and inhibitor EMTP ligand drug, we have performed molecular docking and molecular dynamics (MD) simulations. Docking binding affinities and the formation of a good number of hydrogen bonds suggest that EMTP appears to be a promising drug for the selected inhibitors.

Linear, Second-Order Accurate, and Energy Stable Scheme for a Ternary Cahn–Hilliard Model by Using Lagrange Multiplier Approach

We develop a second-order accurate, energy stable, and linear numerical method for a ternary Cahn–Hilliard (CH) model. The proposed scheme is an extension of typical Lagrange multiplier approach for binary CH system. The second-order backward difference formula (BDF2) is applied to construct time discretization. We theoretically prove the mass conservation, unique solvability, and energy stability of the proposed scheme. We efficiently solve the resulting discrete linear system by using a multigrid algorithm. The numerical solutions demonstrate that the proposed scheme is practically stable and second-order accurate in time and space. Moreover, we can use the proposed scheme as an effective solver to calculate the ternary CH equations in ternary phase-field fluid systems.

Structural (X-ray), spectroscopic (FT-IR, FT-Raman) and computational (DFT) analysis of intermolecular interactions in 1H-indazole-3-carbaldehyde

The title compound, 1H-indazole-3-carbaldehyde, C8H6N2O (1) is important as it represents a rare example of indazole found in nature. The asymmetric unit of 1 consists of two independent molecules (1A and 1B) which are linked by N—H⋅⋅⋅O hydrogen bonds (N⋅⋅⋅O = 2.8178(15) Å and 2.8203(14) Å), forming one-dimensional chains. The crystal structure is stabilized by slipped face-to-face π⋅⋅⋅π interactions (Cg⋅⋅⋅Cg distances in the range 3.8492(8) – 4.1830(8) Å), C=O⋅⋅⋅π interactions (O⋅⋅⋅centroids distances in the range 3.3252(12) – 3.4795(11) Å) and weak non-classical C—H⋅⋅⋅N hydrogen bonds (C⋅⋅⋅N = 3.4377(18) Å). 3D Hirshfeld surface analysis, 2D fingerprint plots and molecular electrostatic potentials were applied for a detailed investigation of all the interactions participating in the crystal packing. The intermolecular interactions were also confirmed by Natural Bond Orbital (NBO) analysis at the B3LYP and B3LYP-D3 levels using the 6-31++G(d,p) basis set. The energies of the intermolecular interactions (the second-order interaction energies, E2) oscillate between 55.5 kJ⋅mol−1 and 22.3 kJ⋅mol−1 for strong N−H⋅⋅⋅O hydrogen bond. The E2 value for the C=O⋅⋅⋅π and π⋅⋅⋅π interactions are about 4.9 kJ⋅mol−1 and 3.6 kJ⋅mol−1, respectively. Moreover, the strength of the hydrogen bonds was evaluated using vibrational spectroscopy (FT-IR and FT-Raman) and DFT calculations at the B3LYP level within the 6-31++G(d,p) basis set. These studies additionally confirm the presence of various intermolecular interactions in the crystal of 1.

Spectroscopic and DFT investigations of 8-hydroxy quinoline-5-sulfonic acid-5-chloro-8-hydroxyquinoline cocrystal

In this study, solvent-assisted co-grinding method is used to form the cocrystal of 8-hydroxy quinoline-5-sulfonic acid (HQS) and 5-chloro-8-hydroxyquinoline (CHQ). In order to determine spectroscopic and electronic properties, the theoretical characterization has been carried out. Charge delocalization patterns and second-order perturbation energies of the most interacting orbitals have also been computed and predicted. Geometrical parameters are in agreement with reported values. Molecular electrostatic potential plot predicts the reactive sites and electropositive potential region is around the hydrogen atom bonded through the nitrogen atoms, negative potentials on oxygen atoms and phenyl rings. Molecular docking of the study of the HQS-CHQ molecule has been performed for the receptors, 3C52, 4IIT, 3QYD and 4FGY.

A non-empirical intermolecular force-field for trinitrobenzene and its application in crystal structure prediction.

An anisotropic atom-atom distributed intermolecular force-field (DIFF) for rigid trinitrobenzene (TNB) is developed using distributed multipole moments, dipolar polarizabilities, and dispersion coefficients derived from the charge density of the isolated molecule. The short-range parameters of the force-field are fitted to first- and second-order symmetry-adapted perturbation theory dimer interaction energy calculations using the distributed density-overlap model to guide the parameterization of the short-range anisotropy. The second-order calculations are used for fitting the damping coefficients of the long-range dispersion and polarization and also for relaxing the isotropic short-range coefficients in the final model, DIFF-srL2(rel). We assess the accuracy of the unrelaxed model, DIFF-srL2(norel), and its equivalent without short-range anisotropy, DIFF-srL0(norel), as these models are easier to derive. The model potentials are contrasted with empirical models for the repulsion-dispersion fitted to organic crystal structures with multipoles of iterated stockholder atoms (ISAs), FIT(ISA,L4), and with Gaussian Distributed Analysis (GDMA) multipoles, FIT(GDMA,L4), commonly used in modeling organic crystals. The potentials are tested for their ability to model the solid state of TNB. The non-empirical models provide more reasonable relative lattice energies of the three polymorphs of TNB and propose more sensible hypothetical structures than the empirical force-field (FIT). The DIFF-srL2(rel) model successfully has the most stable structure as one of the many structures that match the coordination sphere of form III. The neglect of the conformational flexibility of the nitro-groups is a significant approximation. This methodology provides a step toward force-fields capable of representing all phases of a molecule in molecular dynamics simulations.

Electronic transport behavior of 1-(Phenyldiazenyl)naphthalen-2-ol and its derivatives as optical molecular switches: A first-principles approach

We studied the electronic transportation properties of 1-(Phenyldiazenyl)naphthalen-2-ol and its derivatives, as optical molecular switches, by using the nonequilibrium Green’s function (NEGF) formalism combined with the first-principles density functional theory (DFT). To describe this switching, we applied the geometrical and topological parameters, Time-dependent density functional theory (TD-DFT), and the second-order interaction energies, E(2), results. The mentioned switching for titled molecules occurred between their tautomers, hydrazo and azo forms, upon photoexcitation. According to our results the current rate of titled molecules is more than that the other reported molecules, about 40,000 nA. Therefore, titled molecules show appropriate potential for using in molecular switch tools. The transmittance spectra and I–V curves show the current of the azo tautomer is more than that in the hydrazo tautomer. This result agree with increasing of the intramolecular hydrogen bond strength, electron densities of aromatic and chelated rings, and the hyperconjugations in the azo forms. In addition, the −OCH3 and -NO2 groups, does not remarkably affected the current rate with Y (111) (Y =Au, Ag, and Pt) electrodes. The best performance obtained in Ag electrode, in while in the other reported molecular switchers Au electrode was appropriated.

Energy poverty measures and the identification of the energy poor: A comparison between the utilitarian and capability-based approaches in Chile

This work explores the consequences that different energy poverty definitions and measures might have for the identification of the energy poor. Using the 2017 National Survey of Public Energy Perception applied to a sample of 3,500 households in Chile, we compare the respective identification outcomes of applying the ten percent rule index (TPRI) and our proposed Perception-based Multidimensional Energy Poverty Index (PMEPI) against the monetary poverty identification outcome. Based on the findings of this comparation, we propose a classification system of first- and second-order energy poverty measures depending on their degree of association with income poverty (as indicated by the distribution of the income poverty status of households). A first-order energy poverty measure exhibits a high association level with income poverty. By contrast, a second-order energy poverty measure shows a low level of association. Coincidentally, our TPRI (first-order) and PMEPI (second-order) estimates each classify 15.5% of the population as energy poor. However, the adoption of any particular definition necessarily narrows the resulting set of energy-poor households in a way that is distinct from other definitions, meaning that the use of multiple definitions produces diverging energy poverty rankings across the territory. Moreover, the TPRI neglects supply-side constraints captured by the PMEPI. Consequently, when identifying and targeting the energy poor, first- and second-order definitions should not be used as substitutes but rather as complements. This fact needs to be considered in the energy policy debate on the implementation of energy poverty alleviation actions.