Density Isosurface Research Articles

Mechanisms of C(sp3)-H Functionalization of Acetonitrile or Acetone with Alkynes: A DFT Investigation.

The mechanisms for the C(sp3)-H activation and addition reactions between acetonitrile (or acetone) and alkynes have been investigated with the M06-2X-D3/ma-def2-TZVP method and basis set. The SMD (solvation model based on solute electron density) model was applied to simulate the solvent effect. In the first and second reactions, 2-phenylbut-3-yn-2-ol reacted with acetonitrile and acetone, respectively. First, the C(sp3)-H activations of acetonitrile and acetone could be achieved by PhCOO• and t-BuO• radicals. Then, addition reactions converted 2-phenylbut-3-yn-2-ol into final products P1 and P2. Gibbs free energy surfaces of these two reactions suggest that blue lines would be the favorable paths with lower Gibbs energy barriers, and the terminal C atom of the C≡C bond is the best reactive site. Moreover, the analysis of the IRI (Interaction Region Indicator) reveals the Z- and E-configuration transformations. While in the third and fourth reactions, methyl(2-(phenylethynyl)phenyl)sulfane has interactions with acetonitrile and acetone via some paths, respectively. Gibbs free energy profiles show that the C10 atom, rather than the C11 atom, has priority, and the blue lines are favorable. Furthermore, the action mode of Na2HPO4 could reduce the energy barrier and benefit the reaction. vdW (van der Waals) interactions play an important role in the choice for the reactive site. In the fifth (or sixth) reaction, it happened between 1-(2-(methylthio)phenyl)-3-phenylprop-2-yn-1-one and acetontrile (or acetone) to yield the final product P5 (or P6). The computational results uncovered the blue line is the best path, and the choice for the reactive site depends on the vdW interactions, which reveals the origin of selectivity. In addition, the investigation for the byproducts have been carried out, and these can explain the reason that only the main product is produced. Both of those can agree with the experimental results. The localized orbital locator (LOL) isosurfaces, Laplacian bond order (LBO), electron density of the bond critical point (ρBCP), electron spin density isosurface graphs, and IRI graphs can be used to analyze the structure and reveal the reaction substances.

Evolution of metallicity, enhancement of [formula omitted] and magnetic anisotropy energy in Y[formula omitted]NiIrO[formula omitted]: Hydrostatic ([111]) strain influence

Ir-based double perovskite oxides (DPO) provide a distinct electronic and magnetic behavior due to entanglement among lattice distortion, strong electron correlation, and spin–orbit coupling (SOC). In this work, we investigated the hydrostatic ([111]) strain impact on the physical properties of the Y2NiIrO6 DPO using ab-initio calculations. Unstrained motif displayed the ferrimagnetic (FiM) spin state owing to strong antiferromagnetic (AFM) interactions between Ni↑ and Ir↓ ions, further confirmed by the computed partial spin magnetic moments and 3D spin-magnetization density iso-surfaces plots. A Mott-insulating state is established with an energy band gap (Eg) of 0.43 eV due to the existence of a rare Ir+4 state having Jeff.=12 and a Curie temperature (TC) of 198 K using the Heisenberg Hamiltonian model, which is up to the experimental observations. The easy magnetic axis is the [010] (b-axis) having a giant magnetic anisotropy energy (MAE) constant of 1.7 × 108 erg/cm3. Moreover, it is predicted that strain holds the FiM spin order as a magnetic ground state for the considered range of ±8%. Notably, an electronic transition from Mott-insulating to a metallic state is established at a critical compressive strain of −8%, where the admixture of Ir 5d states appears at/around the Fermi level. On the other hand, Eg solely increases with the increase of tensile strain amplitude. Due to strong and weak hybridization, the spin/orbital magnetic moment value is reduced and enhanced as a function of compressive and tensile strains, respectively. Along with this, it is found that MAE/TC increases to 25%/18% and 15%/10% at −8% compressive and ＋8% tensile strains due to larger structural distortion than that of the unstrained one, which enhances the system potential for magnetic memory devices.

Introducing KICK-MEP: exploring potential energy surfaces in systems with significant non-covalent interactions.

Exploring potential energy surfaces (PES) is fundamental in computational chemistry, as it provides insights into the relationship between molecular energy, geometry, and chemical reactivity. We introduce Kick-MEP, a hybrid method for exploring the PES of atomic and molecular clusters, particularly those dominated by non-covalent interactions. Kick-MEP computes the Coulomb integral between the maximum and minimum electrostatic potential values on a 0.001 a.u. electron density isosurface for two interacting fragments. This approach efficiently estimates interaction energies and selects low-energy configurations at reduced computational cost. Kick-MEP was evaluated on silicon-lithium clusters, water clusters, and thymol encapsulated within Cucurbit[7]uril, consistently identifying the lowest energy structures, including global minima and relevant local minima. Kick-MEP generates an initial population of molecular structures using the stochastic Kick algorithm, which combines two molecular fragments (A and B). The molecular electrostatic potential (MEP) values on a 0.001 a.u. electron density isosurface for each fragment are used to compute the Coulomb integral between them. Structures with the lowest Coulomb integral are selected and refined through gradient-based optimization and DFT calculations at the PBE0-D3/Def2-TZVP level. Molecular docking simulations for the thymol-Cucurbit[7]uril complex using AutoDock Vina were performed for benchmarking. Kick-MEP was validated across different molecular systems, demonstrating its effectiveness in identifying the lowest energy structures, including global minima and relevant local minima, while maintaining a low computational cost.

Exploring the Diversity and Dehydration Performance of New Mixed Tutton Salts (K2V1−xM’x(SO4)2(H2O)6, Where M’ = Co, Ni, Cu, and Zn) as Thermochemical Heat Storage Materials

Tutton salts form an isomorphic crystallographic family that has been intensively investigated in recent decades due to their attractive thermal and optical properties. In this work, we report four mixed Tutton crystals (obtained by the slow solvent evaporation method) with novel chemical compositions based on K2V1−xM’x(SO4)2(H2O)6, where M’ represents Co, Ni, Cu, and Zn, aiming at thermochemical energy storage applications. Their structural and thermal properties were correlated with theoretical studies. The crystal structures were solved by powder X-ray diffraction using the Rietveld method with similar compounds. All of the samples crystallized in monoclinic symmetry with the P21/a-space group. A detailed study of the intermolecular interactions based on Hirshfeld surfaces and 2D fingerprint mappings showed that the main interactions arise from hydrogen bonds (H∙∙∙O/O∙∙∙H) and dipole–ion (K∙∙∙O/O∙∙∙K). On the other hand, free space percentages in the unit cells determined by electron density isosurfaces presented low values ranging from 0.53 (V–Ni) to 0.81% (V–Cu). The thermochemical findings from thermogravimetry, a differential thermal analysis, and differential scanning calorimetry indicate that K2V0.47Ni0.53(SO4)2(H2O)6 salt is the most promising among mixed salts (K2V1−xM’x(SO4)2(H2O)6) for heat storage potential, achieving a low dehydration temperature (≈85 °C), high dehydration enthalpy (≈360 kJ/mol), and high energy storage density (≈1.84 GJ/m3).

Electron iso-density surfaces provide a thermodynamically consistent representation of atomic and molecular surfaces

The surface area of atoms and molecules plays a crucial role in shaping many physiochemical properties of materials. Despite its fundamental importance, precisely defining atomic and molecular surfaces has long been a puzzle. Among the available definitions, a straightforward and elegant approach by Bader describes a molecular surface as an iso-density surface beyond which the electron density drops below a certain cut-off. However, so far neither this theory nor a decisive value for the density cut-off have been amenable to experimental verification due to the limitations of conventional experimental methods. In the present study, we employ a state-of-the-art experimental method based on the recently developed concept of thermodynamically effective (TE) surfaces to tackle this longstanding problem. By studying a set of 104 molecules, a close to perfect agreement between quantum chemical evaluations of iso-density surfaces contoured at a cut-off density of 0.0016 a.u. and experimental results obtained via thermodynamic phase change data is demonstrated, with a mean unsigned percentage deviation of 1.6% and a correlation coefficient of 0.995. Accordingly, we suggest the iso-density surface contoured at an electron density value of 0.0016 a.u. as a representation of the surface of atoms and molecules.

Probing the metallic state, magnetic anisotropy, and large Curie temperature in CaCuFeReO[formula omitted]: Strain engineering

Rhenium-based double perovskite oxides (DPOs) are a particularly fascinating class of materials because of high carrier spin polarization, large magnetic anisotropy energy (MAE), and complex electrical behavior along with high Curie temperature (TC). Herein, we discussed the impact of biaxial ([110]) strain ranging from −5% to ＋ 5% along the ab-plane on the electronic and magnetic properties of CaCuFeReO6 (CCFRO) DPO using ab-inito calculations. The unstrained system exhibits a ferrimagnetic (FiM) spin ordering as an energetically stable magnetic ground state due to electron hopping between Fe+3/Re+5t2g and Cu+2eg orbitals along with a metallic electronic state. Moreover, [010] (b-axis) is the magnetic easy axis that produces the MAE of 5.36 meV, giving a giant MAE constant of 1.97×107 erg/cm3. The evaluated partial spin-magnetic moment on the Cu1/Cu2/Fe/Re ion is 0.14/0.44/4.04/−0.64μB, where “−” sign on the Re moment means that its spin is antiparallel to the other ions, verifying the FiM ordering in the system. Also, the eg, t2g/eg, and t2g orbital characteristics of Cu+2, Fe+3, and Re+5 ions are visible in the spin-magnetization density iso-surfaces plots, respectively. Using the classical Heisenberg model, the computed TC for the unstrained structure is 576 K, which is quite close to the experimentally reported value of 567 K. In addition, it is shown that the FiM metallic behavior in the motif is robust against biaxial ([110]) strain within the considered range. It has also been revealed that TC increased to 5.73%/3.30% for the considered range of −5% compressive/＋5% tensile strain due to improved structural distortions.

Quantum chemical computational analysis, electronic transitions, interaction mechanisms analysis by spectroscopic, molecular docking, and molecular dynamic simulation of retinol

Quantum computational simulations based on density functional theory are employed to investigate the molecular structure of Retinol. Both geometrical parameters and electronic transitions for gas and green solvents are calculated. Characteristic frequencies were identified and band assignments were achieved through normal coordinate analysis. The calculated spectra and a comparative study of the vibrational spectra, which included a variety of vibration modes, were compared with the experimental spectra. A compound’s strong reactivity may be indicated by the bandgap, which also indicates the possibility of further charge exchange through the molecule. Determination of relative electrophilicity/nucleophilicity indices of retinol was undertaken through the prediction of condensed Fukui functions, complemented by the generation of molecular electrostatic potential surface maps. This exploration was validated through meticulous correlation with reduced density gradient and isodensity surface plots. The docking analysis of retinol with different proteins was performed to confirm anti-inflammatory activity. To gain comprehensive insights into macromolecule pliability concerning protein–ligand interactions, an effective molecular dynamics simulation was conducted.

Density functional theory analysis of the stability of H[formula omitted]O and CO[formula omitted]-derived surface species over low-index Ni facets

Analysis of stability of chemical species over catalytic surfaces is crucial for understanding the surface-specific effects to reach optimal catalyst composition. With reference to CO2 hydration, we undertook the task of unravelling the same over Ni surfaces, and examined the effect of exposed surface facets on the stability of relevant surface species. By examining H2O and CO2-derived surface species over Ni(100), Ni(110), and Ni(111) surface facets, we investigated the adsorption and dissociation of H2O and CO2-derived surface, enabling a thorough comparison of facet effects. A linear scaling relationship between the adsorption energy of the adsorbates and Bader charges was observed, providing an evidence that the binding energy of surface species originating from H2O and CO2 was closely correlated to the degree of electron transfer from Ni to the adsorbed species. Understanding of the binding and stability of H2O and CO2-derived species over Ni surfaces was furthered by the analysis of the charge density iso-surfaces. Stability plots and reaction paths highlighted Ni(100) and Ni(110) to be superior to Ni(111). Ni(110) exhibited the lowest H2O dissociation barrier, while Ni(100) showed favourable CO2 dissociation barriers citing Ni(110) surface facet as the most suited plane for selective CO2 hydration.

Density structure of Kīlauea volcano: implications for magma storage and transport

SUMMARYA Bayesian linear regression to determine the bias in the Nafe–Drake relationship between compressional velocity and density provides an improved model for the density structure of Kīlauea volcano, Hawaiʻi. In previous work, we combined the results of seismic tomography with the Nafe–Drake relationship between compressional velocity and density to explain the large values of gravity disturbances overlying the summits and rift zones of the island's volcanoes. These results were used to determine mechanisms for gravitational instability of the island flanks. Here, we use laboratory measurements of the relationship of velocity and density for a wide range of Hawaiʻi island rocks as a prior in a Bayesian regression, with seismic tomography, to refine the 3-D density structure for Kīlauea volcano. This refined structure shows dense bodies (3220 kg m−3) between 5 and 8 km below sea level that underly regions of magma storage, found from geodetic and geophysical studies, beneath the summit and East Rift Zone of Kīlauea volcano. Above these bodies, density isosurfaces surround and cradle sources of pressure change determined from geodetic models, both at the summit and along the East Rift Zone. Continued subsidence of the summit following the 2018 eruption is aligned with a bowl-shaped density structure, formed primarily by density isosurfaces between 2800 and 2900 kg m−3 at 4–6 km depth. These surfaces underly the ∼3 km depth at which dyke injection initiates, are largely aseismic, and from their density values are inferred to contain high concentrations of olivine. Taken together, these density structures are consistent with an olivine-rich mush with variable porosity that increases in density with depth and provides a mechanism to form olivine cumulates both at the summit and along the rift zones. This structural framework for Kīlauea volcano is consistent with melt and mush transport occurring over a large range of depths to accommodate the growth and spreading of the volcano.

3-D probability density imaging of Euler solutions using gravity data: a case study of Mount Milligan, Canada

Euler deconvolution is a widely used automatic or semi-automatic method for potential field data. However, it yields many spurious solutions that complicate interpretation and must be reduced, eliminated, recognized, or ignored during interpretation. This study proposes a post-processing algorithm that converts Euler solutions produced by tensor Euler deconvolution of gravity data with an unprescribed structural index into probability values (p values) using the B-spline series density estimation (BSS) method. The p values of the Euler solution set form a probability density distribution on the estimation grid. The BSS method relies on the fact that while spurious solutions are sparse and ubiquitous, Euler deconvolution yields many similar or duplicate solutions, which may tightly cluster near real sources. The p values of the Euler solution clusters form multi-layered isosurfaces that can be used to discriminate neighboring target sources because the p values of spurious solutions are vanishingly small, making it simple to remove their interference from the probability density distribution. In all synthetic cases, the geometric outlines of anomaly sources are estimated from probability density isosurfaces approximating synthetic model parameters. The BSS method was then applied to airborne gravity data from Mount Milligan, British Columbia, Canada. Subsequently, results from synthetic models and field data show that the proposed method can successfully localize meaningful geological targets.

Probing intramolecular interactions using molecular electrostatic potentials: changing electron density contours to unveil both attractive and repulsive interactions.

We focus on intramolecular interactions, using the electrostatic potential plotted on iso-density surfaces to lead the way. We show that plotting the electrostatic potential on varying iso-density envelopes much closer to the nuclei than the commonly used 0.001 a.u. contour can reveal the driving forces for such interactions, whether they be stabilizing or destabilizing. Our approach involves optimizing the structures of molecules exhibiting intramolecular interactions and then finding the contour of the electronic density which allows the interacting atoms to be separated; we call this the nearly-touching contour. The electrostatic potential allows then to identify the intramolecular interactions as either attractive or repulsive. The discussed 1,5- and 1,6-intramolecular interactions in o-bromophenol and o-nitrophenol are attractive, while the interactions between terminal methyl hydrogens in diethyl disulfides (as shown recently) and those between the closest hydrogens in planar biphenyl and phenanthrene are clearly repulsive in nature. For the attractive 1,4-interactions in trinitromethane and chlorotrinitromethane, and the 1,3-S⋯N and the 1,4-Si⋯N interactions in the ClH2Si(CH2)nNH2 series, the lack of (3,-1) bond critical points has often been cited as reason to not identify such interactions as attractive in nature. Here, by looking at the nearly-touching contours we see that bond critical points are neither necessary nor sufficient for attractive interactions, as others have pointed out, and in some instances also pointing to repulsive interactions, as the examples of planar biphenyl and phenanthrene discussed in this work show.

DFT investigation of the DDQ-catalytic mechanism for constructing C-O bonds.

In this study, we investigated the photo-catalytic mechanisms for the construction of C-O bonds from arenes (benzene, 2',6'-dimethyl-[1,1'-biphenyl]-2-carboxylic acid, or 2,4-dichloro-1-fluorobenzene), catalyzed by 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ). All the structures for the Gibbs free surfaces were calculated at the M06-2X-D3/ma-def2-SVP level in the SMD solvent model. Also, TDDFT calculations of DDQ were performed at the PBE1PBE-D3/ma-def2-SVP level in the SMD solvent model. The computational results indicated that DDQ, serving as a photo-catalyst, would be excited under visible light of 450 nm, aligning well with experimental observations as reflected in the UV-vis spectrum. Gibbs free energy surface analyses of the three reactions suggested that the path involving 3DDQ* activating the reactant (-COOH, H2O, or CH3OH) is favorable. Additionally, the role of O2 was investigated, revealing that it could facilitate the recycling of DDQ by lowering the energy barrier for the conversion of the DDQH˙ radical (not DDQH2) into DDQ. The use of ρhole and ρele can reveal the photo-catalytic reaction and charge transfer processes, while localized orbital locator isosurfaces and electron spin density isosurface graphs were employed to analyze structures and elucidate the single electron distribution. These computational results offer valuable insights into the studied interactions and related processes, shedding light on the mechanisms governing C-O bond formation from arenes catalyzed by DDQ.

Insulator-to-metal transition, magnetic anisotropy, and improved TC in a ferrimagnetic La2CoIrO6: strain influence.

The elegant interactions between Coulomb repulsion and spin-orbit coupling in Ir-based double perovskite oxides (DPO) normally induce peculiar magnetic behavior. Herein, we investigate the effect of the development of biaxial [110] strain on the formation energetics, and electronic and magnetic properties of the La2CoIrO6 DPO employing density functional theory calculations. Our results reveal that the unstrained motif is a Mott-insulator achieving an energy band gap of 0.35 eV with a ferrimagnetic (FiM) ground state, which essentially arises due to anti-ferromagnetic (AFM) coupling between the half-occupied Co t2g and partially occupied Ir t2g/empty eg orbitals via oxygen 2p states. Along with this, it is found that [001] (c-axis) is the easy magnetic axis, which results in 12.5 meV total energy per u.c., obtaining a large anisotropy constant of 0.8 × 108 erg cm-3. The computed partial spin-magnetic moments on the Co/Ir ion are 2.64/-0.46 μB, where the negative sign on the Ir ion moment confirms the AFM interactions between them. Additionally, the t2g/eg and t2g orbital characteristics of Co2+ and Ir4+ ions are visible in the spin-magnetization density isosurfaces plot, respectively. Likewise, the estimated Curie temperature (TC) using the Heisenberg model is 104 K, which is in agreement with the experimentally observed value of 94/97 K. Interestingly, an insulator-to-metal transition is achieved at a critical compressive strain of -6% with a robust FiM state, where the Co 3dxy and Ir 5dx2-y2 orbitals are mainly responsible for metallicity. Simultaneously, the magnetocrystalline anisotropy energy and TC can be sufficiently enhanced by applying compressive strain due to enhancement in the structural distortions. So this work suggested that the strain strategy is an efficient approach to tuning the properties of the compounds for their feasible realization in spintronics.

Boiling, critical, and freezing temperatures in light of molecular descriptors: correlation and causation.

In the pursuit of tracking some physicochemical properties of fluids down to the molecular level, ab initio molecular surface analyses were performed on 169 molecules. This included electrostatic potential (EP), average local ionization energy (ALIE), and electron localization function (ELF) mapped onto an electron density isosurface value of 0.001 au. Using stepwise linear regression (SLR) analysis, it was found that besides the well-studied EP, ALIE and ELF played important roles in determining the normal boiling and freezing points and critical temperatures of fluids. Apparently, the ALIE and ELF were relevant to the attractive polarization forces and repulsive Pauli forces, respectively, between molecules. To further demonstrate and rationalize this assumption, a localized molecular orbital energy decomposition analysis (LMO-EDA) was carried out. In the LMO-EDA analysis, the complexes of the helium atom, He, and ClCl, ClBr, ClI, OCO, OCS, OCSe, and CO/OC molecules were investigated, where the helium atom faced different molecular sites in each molecule. Fortunately, the results showed that lower the ALIE value on a molecular site, the stronger (i.e., more attractive) the polarization interaction energy. The results also indicated that higher the ELF value on a molecular site, the stronger (i.e., more repulsive) the Pauli interaction. The work is aimed to present novel molecular-based rationales to physical chemists, chemical engineers, and materials scientists.

Pressure-induced structural and magnetic ordering transitions in the J1-J2 square lattice antiferromagnets AMoOPO4Cl (A = K, Rb).

By means of ab initio density functional theory calculations taking into account electronic correlation and van der Waals force, we conducted comprehensive studies of the electronic and magnetic properties, as well as structural and magnetic ordering evolution under pressure of the square lattice antiferromagnets AMoOPO4Cl (A = K, Rb) containing Mo5+ ions with , theoretically predicted as the potential candidates for achieving quantum phases, existing in the boundary regimes for square lattice magnets. Our results indicate that the columnar antiferromagnetic ordering, experimentally determined, is the magnetic ground state of the ambient P4/nmm phase, stabilized by the predominant antiferromagnetic next nearest neighbor interaction J2 in the diagonal directions of the square lattice, regardless of the effective Hubbard amendment values. More importantly, the P4/n phase, involving the mutual twisting of the MoO5Cl and PO4 polyhedra, satisfactorily reproduces the experimentally observed structural transition and the subsequent magnetic ordering transition from columnar antiferromagnetic ordering to Néel antiferromagnetic one, identified to be the appropriate high pressure structure. Furthermore, the mechanism underlined responsible for the magnetic ordering transition at high pressure has been disclosed in terms of density of states and spin density isosurface analysis across the transition. The loss of mirror plane symmetry in the P4/n phase activates the P 3s orbitals to participate in the magnetic interaction, giving rise to a competitive ferromagnetic superexchange interaction, in addition to antiferromagnetic direct one, and consequently initiating the magnetic ordering transition. The insights revealed here not only deepen our understanding of the electronic properties and structural and magnetic ordering transitions under high pressure of square lattice antiferromagnets AMoOPO4Cl (A = K, Rb), but also push the boundaries of knowledge by recognizing the role of nonmagnetic ions P 3s in magnetic exchange coupling.

Reaction mechanism of acetonitrile, olefins, and amines catalyzed by Ag2CO3: A DFT investigation

AbstractThe mechanism of Ag2CO3‐catalyzed reactions of acetonitrile, olefins, and amines was investigated by using the M06‐L‐D3/6‐311 + G(d,p) method and level, and solvation model based on solute electron density (SMD) model was applied to simulate the solvent effect. Calculations show that the Ag2CO3 could achieve the Csp3‐H activation by coordinating with the terminal nitrogen atom of CH3CN; then, the addition reaction happened between the obtained Ag‐complex intermediate and olefin via the coordination of Ag and benzene ring; finally, the obtained radical intermediate continues to go through one single electron transfer (SET) process, addition reaction, and H‐shift reaction to yield the final product. The computational results reveal that Fe3+ cation would have assisted the SET process successfully and the path of direct addition with the amine is the optimal. Fukui function and dual descriptor can be used to predict the reactive sites, and electron spin density isosurface graphs can analyze the structures and reveal the substances.

Crustal structure of onshore-offshore Atlantic Canada and environs from constrained 3-D gravity inversion using variable mesh depths

SUMMARYAtlantic Canada encompasses geological evidence of the orogenic and rifting episodes that inspired the development of the theory of plate tectonics and the fundamental concept of the Wilson cycle. To provide a regional crustal-scale view that can complement surface mapping studies and sparse seismological investigations, an onshore–offshore 3-D constrained gravity inversion methodology is proposed involving incorporation of topography and an inversion mesh that is laterally variable in terms of its maximum depth extent. A 3-D density anomaly model for the entirety of Atlantic Canada and its environs is generated, with the inverted density distribution structure and extracted isodensity surfaces showing excellent correspondence with independent and co-located controlled source and passive seismic constraints. The full density model and crustal thicknesses from this work are made freely available so that they may be used for further study, for instance as inputs for deformable plate reconstruction modelling.

Intramolecular Repulsion Visible Through the Electrostatic Potential in Disulfides: Analysis via Varying Iso-density Envelopes.

For a series of diethyl disulfide conformations, the nearly touching contours of the electrostatic potential plotted on iso-density molecular surfaces allow the assessment of intramolecular repulsion. The electrostatic potential is plotted on varying iso-density envelopes to find the nearly touching contours for which (a) the surface electrostatic potential does not show overlap between atoms or functional groups and (b) the typical features are visible (σ-hole, lone pair, hydrogen VS,max). When these nearly touching contours X are closer to the nuclei, the more electron density is excluded from the iso-density envelopes and the smaller are the volumes corresponding to these envelopes. Both the contours X and the corresponding volumes are found to correlate with relative conformational energy, reflecting the degree of intramolecular repulsion present in the various diethyl disulfides. Quantitative estimates of intramolecular repulsion can be made based on relationships between the nearly touching contour X vs relative energy and volume (of the nearly touching contour X) vs relative energy, obtained for series of diethyl disulfide conformers. These relations were used to analyze intramolecular repulsion in a set of disulfides broader than diethyl disulfide conformers. We have shown that the approach of varying electronic density contours can be used in the study of repulsive intramolecular interactions, hereby extending earlier work involving attractive intermolecular interactions.

Towards a classification of charge-3 monopoles with symmetry

We classify all possible charge-3 monopole spectral curves with non-trivial automorphism group and within these identify those with elliptic quotients. By focussing on elliptic quotients the transcendental constraints for a monopole spectral curve become ones regarding periods of elliptic functions. We construct the Nahm data and new monopole spectral curves with D_6 and V_4 symmetry, the latter based on an integrable complexification of Euler’s equations, and for which energy density isosurfaces are plotted. Extensions of our approach to higher charge and hyperbolic monopoles are discussed.

Spectroscopic characterization, DFT study, topological, molecular docking and pharmacological analysis of Iminodiacetic acid Hydrochloride

Iminodiacetic Acid Hydrochloride (IAH) optimum geometries and vibration spectra have been determined by density functional theory computations at B3LYP with 6-311++G(d, p) level basis functions. Finding the most stable structure of IAH is done through conformational analysis. In order to interpret IR and Raman spectra both quantitatively and qualitatively, vibrational spectra have been examined based on the potential energy distribution (PED) within each vibrational mode. By means of calculations both theoretical and experimental, UV–Visible and NMR spectral studies of IAH have been performed. Utilising NBO analysis, stabilisation resulting from inter- and intramolecular interaction has been studied. For predicting the reactivity and stability of the molecule, chemical reactivity descriptors are computed. Molecule size, shape, electrical potential distribution, and point of chemical reactivity will all be revealed by mapping the charge density isosurface well with electrostatic potential surface (ESP). ELF and LOL maps intended topological aspects of IAH have also been depicted. Additionally, the Natural atomic charge and the hyperconjugative interactions that cause its NLO activity have been predicted. The hyper polarizability values indicate that these compounds could be used in electro-optical applications. IAH is screened for its pharmacological activity. The binding location of the molecule to its target protein has been predicted via a molecular docking study.