Search

Single Atom Catalysts (SACs) have shown that the miniaturization of the active site implies new phenomena like dynamic charge transfer between isolated metal atoms and the oxide. To obtain direct proof of this character is challenging, as many experimental techniques provide averaged properties or have limitations with poorly conductive materials, leaving kinetic measurements from catalytic testing as the only reliable reference. Here we present an integrated Density Functional Theory-Microkinetic model including ground and metastable states to address the reactivity of Pt1/CeO2 for CO oxidation. Our results agree with experimentally available kinetic data in the literature and show that CO oxidation activity of Pt1/CeO2 is tunable via the electronic properties of the support. Particularly, samples with higher n-doping via oxygen depletion should be better in CO oxidation, as they help maintain the active state Pt0 of the catalyst. This provides an alternative strategy for tuning the performance of low-temperature oxidations in single-atom catalysts via charge transfer control. peerReviewed

A computational study for the competitive conversion of glycerol to 1,2-propanediol and 1,3-propanediol is presented, considering a two-step sequence of dehydration followed by hydrogenation. The elementary steps for dehydration, i.e., breaking of C–H followed by C–OH or vice versa, were studied computationally both on the Rh metal surface and the acid-modified ReOH–Rh surface in order to understand the role of the acid promoter. While the acid modifier can catalyze the C–OH cleavage, the activation energy for the C–H cleavage was found to be considerably smaller on both pure and acid-doped Rh(111) surfaces, and breaking the secondary C–H bond is kinetically favored over breaking the terminal C–H bond. This is in complete agreement with experimental protocols favoring the formation of 1,2-propanediol. Another potential feedstock, glycidol, was studied for the epoxide ring opening to yield 1,2-propanediol and 1,3-propanediol, and the reaction was found to be metal-catalyzed even in the presence of acid. peerReviewed

This study is aimed at employing the Molecular Dynamics simulations to assess the phenazopyridine (PHP) adsorption, an analgesic drug, on three new metal-organic frameworks (MOFs); IRMOF-16, HKUST-1, and ZIF-8, with excellent behavior in π−π stacking, H-bonding, and electrostatic interactions. To further decipher the adsorption mechanism of PHP on MOFs, coarse-grained (CG) simulations and density functional theory (DFT) calculations were also exploited. Simulations revealed the PHP adsorption intensity of around 100%, 60%, and 40% by IRMOF-16, HKUST-1, and ZIF-8, respectively. Moreover, CG simulations and DFT calculation validated the superior PHP adsorption capacity of IRMOF-16 with the energy value of -343.4 kJ/mol and -1.53 eV, respectively. Furthermore, the PHP adsorption capability of IRMOF-16 was scrutinized under three distinct modifications: functionalization with hydroxyl functional group, tuning porosity size, and hybrid framework formation with DAAQ-TFP Covalent Organic Frame (COF). Interestingly, the modification of IRMOF-16 with hydroxyl groups and grafting with the COF led to considerably better performance in removing PHP, since their modifications increased the negative net charge of the surface, resulting in greater interactions with the positively charged PHP molecules. Furthermore, enlarging the IRMOF-16 pore size relatively reduced the adsorption functionality, due to the limited interactions of PHPs with available active sites.

Remdesivir has been recognized as an important medicine in the control of COVID-19 illness. Since carbon nanotubes were considered in the design of novel drug delivery vehicles, the interaction between simple CNT, functionalized CNT by carboxylic group and S-, Al-, and Si-doped CNT and Remdesivir drug were studied using density functional theory (DFT) and time dependent DFT (TDDFT) calculations. The results of this work show that the Si-doped CNT is the best drug delivery system for Remdesivir due to its better electronic, energetic, adsorption and thermodynamic properties., Graphical abstract Image 1

Graphical abstract, Highlights • N—H⋯O intermolecular interactions elucidates the effect of hyperconjugation. • C—H⋯O intermolecular interactions elucidates the effect of rehybridization. • FT-IR and FT-Raman spectral analysis substantiates the red shift and blue shift in stretching frequencies. • Drug likeness and ADMET analysis reveals pharmacokinetic properties. • Molecular docking shows the interaction of MCMH with SARS-CoV-2 protease., Prospective antiviral molecule (2E)-N-methyl-2-[(4-oxo-4H-chromen-3-yl)methylidene]-hydrazinecarbothioamide has been probed using Fourier transform infrared (FTIR), FT-Raman and quantum chemical computations. The geometry equilibrium and natural bond orbital analysis have been carried out with density functional theory employing Becke, 3-parameter, Lee-Yang-Parr method with the 6-311G++(d,p) basis set. The vibrational assignments pertaining to different modes of vibrations have been augmented by normal coordinate analysis, force constant and potential energy distributions. Drug likeness and oral activity have been carried out based on Lipinski's rule of five. The inhibiting potency of 2(2E)-methyl-2-[(4-oxo-4H-chromen-3-yl)methylidene]-hydrazinecarbothioamide has been investigated by docking simulation against SARS-CoV-2 protein. The optimized geometry shows a planar structure between the chromone and the side chain. Differences in the geometries due to the substitution of the electronegative atom and intermolecular contacts due to the chromone and hydrazinecarbothioamide were analyzed. NBO analysis confirms the presence of two strong stable hydrogen bonded N—H⋯O intermolecular interactions and two weak hydrogen bonded C—H⋯O interactions. The red shift in N—H stretching frequency exposed from IR substantiates the formation of N—H⋯O intermolecular hydrogen bond and the blue shift in C—H stretching frequency substantiates the formation of C—H⋯O intermolecular hydrogen bond. Drug likeness, absorption, distribution, metabolism, excretion and toxicity property gives an idea about the pharmacokinetic properties of the title molecule. The binding energy of the nonbonding interaction with Histidine 41 and Cysteine 145, present a clear view that 2(2E)-methyl-2-[(4-oxo-4H-chromen-3-yl)methylidene]-hydrazinecarbothioamide can irreversibly interact with SARS-CoV-2 protease.

Noscapine is an alkaloid based on the isoquinoline ring with many promising biological potential. Noscapine and its derivatives have shown potential as cough suppressant, anti-cancerous activity, ability to inhibit the main protease of SARS-CoV-2 and non-structural protease of chikungunya etc. Literature has reported the problem of solubility of noscapine due to high hydrophobic character, therefore, poorly soluble in water. In view of this, there is a need to find way to increase the solubility of noscapines. Ionic liquids (ILs) are organic salts and considered to have no or permissible toxicity. In the present work, authors report the designing of the ionic liquids (ILs) composed of noscapinium as cation with the different anions. Further, the designed noscapine based ionic liquids were studied using density functional theory (DFT) approach and time dependant density functional theory (TD-DFT). The thermo-chemical data of the designed ionic liquids revealed the stability and reactivity of ILs. Further, the IR and UV–visible spectra of the designed ILs were determined and analyzed. Then, the ADME behavior of designed ILs was calculated and studied using online servers. Based on the DFT calculations performed, (R)-5-((S)-4,5-dimethoxy-3-oxo-1,3-dihydroisobenzofuran-1-yl)-4-methoxy-6,6-dimethyl-5,6,7,8-tetrahydro-[1,3]dioxolo[4,5-g]isoquinolin-6-ium trifluoromethanesulfonate (IL4) is found to be most soluble in the water and most stable amongst the designed ILs.

Highlights • Study of the molecular structure of the Atazanavir molecule by DFT method. • Investigation of the electronic properties, MEP and NBO analysis, charges and UV spectrum of the Atazanavir molecule. • The interaction of Atazanavir drug with the Coronavirus was investigated by molecular docking., Atazanavir (ATZ) is an antiviral drug synthesized. ATZ is being investigated for potential application against the Coronavirus 2019-nCoV. To find candidate drugs for 2019-nCoV, we have carried out a computational study to screen for effective available drug ATZ which may work as an inhibitor for the Mpro of 2019-nCoV. In the present work, the first time the molecular structure of ATZ molecule has been studied using Density Functional Theory (CAMB3LYP/6-31G*) in solvent water. The electronic properties, atomic charges, MEP, NBO analysis, and excitation energies of ATZ have also been studied. The interaction of ATZ compound with the Coronavirus was performed by molecular docking studies., Graphical Abstract Image, graphical abstract

The molecule N-((4-aminophenyl)sulfonyl)benzamide was optimized by making use of density functional theory (DFT) with 6-311++G(d,p) basis set. The vibrational frequency and potential energy distribution (PED) of the title compound were calculated and compared with experimental calculations. By using DFT method, the reactivity nature of the molecule was characterized, like as Local reactivity descriptor, Natural bond orbital with a basis set of 6-311++G(d,p), Frontier molecular orbital (FMOs), etc. The electronic properties for HOMO-LUMO, UV-Vis and MEP maps were contemplated by IEFPCM model with various solvation impacts which depends on TD-DFT ((B3LYP for HOMO-LUMO, MEP and M062X for UV)/6-311++G(d,p)) strategies. The Molecular docking analysis reveals the inhibitory nature of title molecule with Aspergillus Niger a fungal protein, SARS CoV-1 and SARS CoV-2 viral proteins. Hence, the present study reveals that the title compound has structural behavior and bioactive (antifungal and antiviral) nature.

With the global epidemic of the COVID-19 virus, extensive and rapid research on drug therapy is underway around the world. In this regard, one of the most widely studied drugs is Favipiravir. Our aim in this paper is to conduct comprehensive research based on the Density Functional Theory (DFT) on the potential of metallofullerenes as suitable drug carriers. The surface interaction of Favipiravir with organometallic compound resulted by doping of the five transition metals of the first row of the periodic table (Ti, Cr, Cr, Fe, Ni, and Zn) was examined in depth to select the most suitable metallofullerenes. First, the adsorption geometries of Favipiravir drug onto each metallofullerene were deeply investigated. It was found that Cr-, Fe-, Ni-doped fullerenes provide the excellent adsorbent property with adsorption energies of -148.2, -149.6, -146.6 kJ/mol, respectively. The Infrared spectroscopy (IR) study was conducted to survey the stretching vibration of bonds involving in the systems, specialty the C=O in the drug, C-M in the metallofullerene, and M-O in the metallofullerene-drug complex. Finally, the UV-vis analysis showed that the absorption spectra for the studied systems may be attributed to the transition from π-π * and/or n - π*., Graphical abstract Unlabelled Image, Highlights • The surface interaction of Favipiravir with different metallofullerenes was deeply investigated. • The comparison of the calculated vibration peaks with those experimentally reported in the literature showed the formation of transition metal-oxygen bonding vibrations • Results of FMO and NBO confirmed the transfer of charge from Favipiravir molecule to the metallofullerenes that refers to the p-type semiconductivity of metallofullerenes. • The results of the UV-vis study showed that the absorption spectra may be attributed to the transition from π-π * and/or n - π *. • The doping of fullerene with the middle elements of the first row of the periodic table (Cr, Fe, and Ni) would be the best structure to adsorb Favipiravir, as a potential drug COVID-19 treatment.

Three 1,2,4-triazole derivatives have been synthesised from hydrazides and 2-(2-hydroxyphenyl)-4H-1,3-benzoaxin-4-one. With the aid of Conceptual Density Functional Theory (CDFT), Molecular Electrostatic Potential (MEP) and Quantum Theory of Atoms in Molecules (QTAIM) analysis, the effect of incorporating para-substituted moieties on the hydrazides were investigated for both successful and unsuccessful reactions, as well as reactivities for the former. 1H- and 13C NMR, FT-IR and HRMS were used to characterize these compounds.

Graphical abstract, The recently emerged COVID-19 virus caused hundreds of thousands of deaths and instigated a widespread fear, threatening the world’s most advanced health security. In 2020, chloroquine derivatives are among the drugs tested against the coronavirus pandemic and showed an apparent efficacy. In the present work, the chloroquine and the chloroquine phosphate molecules have been proposed as potential antiviral for the treatment of COVID-19 diseases combining DFT and molecular docking calculations. Molecular geometries, electronic properties and molecular electrostatic potential were investigated using density functional theory (DFT) at the B3LYP/6-31G* method. As results, we found a good agreement between the theoretical and the experimental geometrical parameters (bond lengths and bond angles). The frontier orbitals analysis has been calculated at the same level of theory to determine the charge transfer within the molecule. In order to perform a better description of the FMOs, the density of states was determined. The molecular electrostatic potential maps were calculated to provide information on the chemical reactivity of molecule and also to describe the intermolecular interactions. All these studies help us a lot in determining the reactivity of the mentioned compounds. Finally, docking calculations were carried out to determine the pharmaceutical activities of the chloroquine derivatives against coronavirus diseases. The choice of these ligands was based on their antiviral activities.

The properties of spherical 1-nm Pd43 nanoparticles confined between single layers of lepidocrocite-TiO2 are studied by means of Density Functional Theory calculations. Sandwich-like intercalation is then compared to the adsorption on a single oxide layer in terms of metal-oxide bond strength, structural distortion of the metal particle and charge transferred from the metal to the oxide. Then, a Pd(111) slab is put in contact to lepidocrocite-TiO2 on either one side or both sides, simulating the creation of extended interfaces. This permits to compare the behavior of small reactive metal particles to their more inert bulk counterpart. It results that intercalated Pd43 species are bound more strongly to the oxide support compared to those adsorbed on a single oxide layer, resulting in more pronounced structural changes and larger charge transfer, a fact with presumable direct consequences on the catalytic activity. The conclusions drawn for small Pd particles are confirmed also in the case of extended interfaces, even though up to a smaller extent.

Novel antiviral active molecule 2- [(4,6-diaminopyrimidin-2-yl)sulfanyl]-N-(4-fluoro- phenyl)acetamide has been synthesised and characterized by FT-IR and FT-Raman spectra. The equilibrium geometry, natural bond orbital calculations and vibrational assignments have been carried out using density functional B3LYP method with the 6-311G++(d,p) basis set. The complete vibrational assignments for all the vibrational modes have been supported by normal coordinate analysis, force constants and potential energy distributions. A detailed analysis of the intermolecular interactions has been performed based on the Hirshfeld surfaces. Drug likeness has been carried out based on Lipinski's rule and the absorption, distribution, metabolism, excretion and toxicity of the title molecule has been calculated. Antiviral potency of 2- [(4,6-diaminopyrimidin-2-yl)sulfanyl]-N-(4-fluoro-phenyl) acetamide has been investigated by docking against SARS-CoV-2 protein. The optimized geometry shows near-planarity between the phenyl ring and the pyrimidine ring. Differences in the geometries due to the substitution of the most electronegative fluorine atom and intermolecular contacts due to amino pyrimidine were analyzed. NBO analysis reveals the formation of two strong stable hydrogen bonded N – H···N intermolecular interactions and weak intramolecular interactions C – H···O and N – H···O. The Hirshfeld surfaces and consequently the 2D-fingerprint confirm the nature of intermolecular interactions and their quantitative contributions towards the crystal packing. The red shift in N – H stretching frequency exposed from IR substantiate the formation of N – H···N intermolecular hydrogen bond. Drug likeness and absorption, distribution, metabolism, excretion and toxicity properties analysis gives an idea about the pharmacokinetic properties of the title molecule. The binding energy -8.7 kcal/mol of the nonbonding interaction present a clear view that 2- [(4,6-diaminopyrimidin-2-yl)sulfanyl]-N-(4-fluoro- phenyl) acetamide can irreversibly interact with SARS-CoV-2 protease., Graphical abstract Unlabelled Image, Highlights • NBO analysis elucidates the effect of hyperconjugation and rehybridization. • FT-IR and FT-Raman Spectral analysis substantiates the formation of intermolecular interactions • Hirshfeld surface analysis reveals mutiple hydrogen bonded interactions • Drug likeness and ADMET analysis reveals pharmacokinetic properties • Molecular docking shows the interaction of DAPF with SARS-CoV-2 protease.

© 2020 Elsevier B.V. Sodium iron hexacyanoferrate (NaFeHCF) has been considered as a potential cathode for sodium-ion batteries owing to its low-cost and easily prepared procedure. However, it is still challenging to achieve long cyclic stability and superior rate capability, and the sodium storage mechanism of sodium-rich NaFeHCF is still elusive. Herein, a sodium-rich NaFeHCF with rhombohedral structure is presented with excellent electrochemical performances within 2.0–4.2 ​V. The specific capacity of ~115 ​mA ​h ​g−1 is obtained by utilizing two plateaus around 2.9 and 4.06 ​V, respectively. Remarkable rate performance from 10 to 4000 ​mA ​g−1 and 1000 cycles with high capacity retention is achieved as well. Synchrotron powder X-ray diffraction (PXRD) and structural refinement reveals that sodium-ions occupy three different sites (interstitial, face and edge) in rhombohedral unit cell, which contribute different capacities on different plateaus during Na+ extractions. Moreover, the rhombohedral structure is well-maintained after long-term Na+ extractions/insertions and reversible phase transitions with small volume variation are observed through in-situ synchrotron PXRD. The kinetic properties of Na+ in rhombohedral unit cell are identified by ab-initio molecular dynamics method and density functional theory calculations, which indicate that Na+ transport on three-dimensional diffusion paths, thus enabling the outstanding rate performance of NaFeHCF.

Density Functional Theory (DFT) and Atomistic Kinetic Monte Carlo is employed in this work to assess the thermodynamic behaviour of the α (BCC) and γ (FCC) allotropes in the iron-nitrogen system. The calculated nitrogen solubility at unit nitrogen activity from (250 < T < 1538°C) is found to be significantly underestimated, beyond the uncertainty range of the calculation, in both phases. The boundary of the α-γ phase change as featured in Lehrer diagrams is calculated within the nitriding potential (0.001 < r_N < 10) and temperature (300 < T < 900°C) ranges. The boundary shows good agreement with experimental data, but the calculated α region is consistently smaller than the data suggests. Motivated by the existence of grain boundaries and other common defects which cause far more unoccupied volume within iron than is expected in idealised lattice structures, the effect of excess vacancy concentrations in varying ranges between 10^{−12} < c_v < 10 at.% on nitrogen solubility and the α-γ phase change is quantified. It is shown how discrepancies between the theoretical ideal crystal and experimental data can be "corrected" by excess vacancies to model the non-ideality of iron lattices in reality, and evidence is given for the validity of this correction.\ud Results are presented in an applied context, allowing opportunities for experimental verification.\ud

ZnO thin-film transistors (TFTs) with scaled channel lengths of 10 μ m, 5 μ m, 4 μ m, and 2 μ m exhibit increasing intrinsic channel electron mobility at a gate bias of 10 V (15 V) from 0.782 cm2/Vs (0.83 cm2/Vs) in the 10 μ m channel length TFT to 8.9 cm2/Vs (19.04 cm2/Vs) for the channel length scaled down to 2 μ m. Current-voltage measurements indicate an n-type channel enhancement mode transistor operation, with threshold voltages in the range of 8 . 4 V to 5 . 3 V, maximum drain currents of 41 μ A/ μ m, 96 μ A/ μ m, 193 μ A/ μ m, and 214 μ A/ μ m at a gate bias of 10 V, and breakdown voltages of 80 V, 70 V, 62 V, and 59 V with respect to channel lengths of 10 μ m, 5 μ m, 4 μ m, and 2 μ m. The channel electron mobility (excluding contact resistance) is extracted by the transmission line method (TLM) from the effective electron mobility (including contact resistance). The contact sheet resistance of 4 . 6 × 10 5 Ω /sq extracted from the measurements, which is 3.5× larger than the contact sheet resistance of 1 . 3 × 10 5 Ω /sq obtained from the DFT calculation and the 1D self-consistent Poisson-Shrodinger simulation, largely limits the drive current in the scaled ZnO TFTs.

Abinit is a material- and nanostructure-oriented package that implements density-functional theory (DFT) and many-body perturbation theory (MBPT) to find, from first principles, numerous properties including total energy, electronic structure, vibrational and thermodynamic properties, different dielectric and non-linear optical properties, and related spectra. In the special issue to celebrate the 40th anniversary of CPC, published in 2009, a detailed account of Abinit was included [Gonze et al. (2009)], and has been amply cited. The present article comes as a follow-up to this 2009 publication. It includes an analysis of the impact that Abinit has had, through for example the bibliometric indicators of the 2009 publication. Links with several other computational materials science projects are described. This article also covers the new capabilities of Abinit that have been implemented during the last three years, complementing a recent update of the 2009 article published in 2016. Physical and technical developments inside the abinit application are covered, as well as developments provided with the Abinit package, such as the multibinit and a-tdep projects, and related Abinit organization developments such as AbiPy . The new developments are described with relevant references, input variables, tests, and tutorials. Program summary Program Title: Abinit Program Files doi: http://dx.doi.org/10.17632/csvdrr4d68.1 Licensing provisions: GPLv3 Programming language: Fortran2003, Python Journal reference of previous version: X .Gonze et al, Comput. Phys. Commun. 205 (2016) 106–131 Does the new version supersede the previous version?: Yes. The present 8.10.3 version is now the up-to-date stable version of abinit , and supercedes the 7.10.5 version. Reasons for the new version: New developments Summary of revisions: • Many new capabilities of the main abinit application, related to density-functional theory, density-functional perturbation theory, GW, the Bethe-Salpeter equation, dynamical mean-field theory, etc. • New applications in the package: multibinit (second-principles calculations)and tdep (temperature-dependent properties) Nature of problem: Computing accurately material and nanostructure properties: electronic structure, bond lengths, bond angles, primitive cell, cohesive energy, dielectric properties, vibrational properties, elastic properties, optical properties, magnetic properties, non-linear couplings, electronic and vibrational lifetimes, etc. For large-scale systems, second-principles calculations, building upon the first-principles results, are also possible. Solution method: Software application based on density-functional theory and many-body perturbation theory, pseudopotentials, with plane waves or wavelets as basis functions. Different real-time algorithms are implemented for second-principles calculations.

In this study we present the crystal structure, spectroscopic and thermal behavior, Hirshfeld surface analysis, and DFT calculations of a new organic-inorganic hybrid compound (C7H8N3)2[CoCl4]. This compound crystallizes in the centrosymmetric space group P 1 ¯ . Single-crystal X-ray diffraction analysis indicates that structure consists of a succession of mixed layers formed by organic cations and inorganic anions parallel to the (001) plane and propagate according to the c-axis. Layers further are assembled into a 3D supramolecular architecture through N-H…Cl hydrogen bonds and π…π interactions. The peak positions of the experimental PXRD pattern are in agreement with the simulated ones from the crystal structure, indicating phase purity of the title compound. The presence of the different functional groups and the nature of their vibrations were identified by ATR-FTIR and FT-Raman spectroscopies. The tetrahedral environment of Co2+ was confirmed by UV–visible spectroscopy, where the spectrum shows three weak absorption bands in the visible range due to d-d electronic transitions 4A2(F) → 4T2(F), 4A2(F) → 4T1(F) and 4A2(F) → 4T1(P) typical of Co(II) coordination compounds. The direct and indirect optical band gap values were determined by Tauc method. The optimized structure and calculated vibrational frequencies were obtained by density functional theory (DFT) using B3LYP functional. TGA and DSC coupled to mass spectrometry (MS) experiments under argon atmosphere in the temperature range (25–950 °C) were carried out in order to determine the thermal stability of the title compound.

We explored electronic spin-dependent physical aspects of ferromagnetic HgCr2Z4 (Z = S, Se) spinels using density functional theory (DFT) for spintronic and energy storage applications. In calculations of structural, electronic, magnetic, and transport aspects, we used Perdew–Burke–Ernzerhof generalized gradient approximation (PBEsol GGA) plus modified Becke-Johnson (mBJ) potential. To calculate structural parameters, we optimized both spinels in the ferromagnetic phase and our predicted data of structural parameters show good comparison with existing experimental data. Also, the calculated negative formation energy confirms the structural stability of the studied spinels. Analyzing ferromagnetic nature of studied spinels based on exchange splitting energy and magnetic parameters, we used mBJ potential to calculate band structure (BS) and density of states (DOS). By exploring DOS, we found the dominant role of electrons spin has been shown by negative indirect exchange energy Δx(pd) values and the fulfillment of the condition Δx(d) > ΔEcry. In addition, exchange constants (N0α and N0β) and magnetic moments were also calculated to ensure their ferromagnetism in studied spinels. Further, the exploration for the influence of electrons spin on electronic transport aspects has been done by investigating electrical and thermal conductivities, Seebeck coefficient, and power factor by using classical Boltzmann transport theory.

The interaction of water vapor with monolayer NiO/Ag(100) was examined using both experimental and computational techniques. Initial film growth was characterized by scanning tunneling microscopy and low energy electron diffraction showing the formation of NiO(1 × 1). X-ray photoelectron spectroscopy (XPS) reveals that the initial film was mainly composed of NiO oxide with a small amount of hydroxyl groups (OH) attributed to the dissociation of background water vapor at highly reactive edge sites. Density functional theory (DFT) reveals that the adsorption of a water monomer on NiO/Ag(100) terrace sites prefers to be in the molecular rather than the dissociate state. XPS results indicate that upon exposing the oxide film to high water vapor pressures (maximum 333.3 Pa), extensive hydroxylation occurs which is attributed to water dissociation at terrace sites. DFT reveals that upon aggregation of water monomers to dimers at the oxide interface the dissociated dimer is energetically stable. The results herein are consistent with previous MgO/Ag(100) studies, further revealing that for certain metal oxides the formation of water dimers at the metal oxide-vapor interface is a key mechanism leading to extensive terrace site hydroxylation.

We report the first quantum chemical description of the initial steps of Ziegler–Natta olefin polymerization catalysis involving all the relevant catalyst components. TiCl4 binds on the (1 0 4) surface of MgCl2 as a binuclear Ti2Cl8 and on the (1 1 0) surface as a mononuclear TiCl4, both binding modes being stabilized by octahedral six-coordination of Ti and Mg. Aluminum alkyl (triethylaluminum) coordinates to the MgCl2 surface via an unsaturated Cl to initiate catalyst alkylation reactions, thermodynamically driven by dimerization of the chlorinated aluminum alkyl. Addition of an internal donor (dimethyl phthalate) greatly stabilizes the (1 0 4) and (1 1 0) surfaces, ending up directing the alkylation reactions to the binuclear (1 0 4) site. External donor (dimethoxydimethylsilane) further assists the process, stabilizing similarly both catalytic surfaces. The spatial requirements of the donors are shown to be greater on the (1 1 0) surface than on the (1 0 4) surface, rationalizing the role of Lewis bases in the stereocontrol of polyolefins., published version, peerReviewed

Since double bonded systems constituted by higher main group elements are necessarily substituted by bulky substituents, in order to protect these structures kinetically, van der Waals interactions are dominant on the resulting bonding energies. This aspect, studied in detail with different density functional methods for a variety of selected disilenes, is compared with the results of MP2 calculations. Throughout a triple-c basis set was used, in order to allow flexible bonding. The bonding energies in the disilenes were characterized by dissociation into singlet silylenes. For the parent disilene the equilibrium was studied in addition with CCSD calculations utilizing Dunning type basis sets. The corrections for dispersion energies on the functionals BP86, PBE, and B3LYP were at times evaluated according to the Grimme approach, and the results compared with the refit double-hybrid functional BP97-D and MP2. They are sizable for the bulky systems. The only known case of reversible silylene-disilene in equilibrium is studied too. This silylene is known in a cis or trans conformation, with a stronger steric stronger congestion in the cis geometry. The dispersion corrections on stability favor to more extent the more encumbered geometries. Overall the calculations indicate that the traditional density functionals, like B3LYP or BP86 are not capable to describe properly the bulky molecular structures. (C) 2010 Elsevier BM. All rights reserved.

3-Fluoroanisole (3-FA) and 3,5-difluoroanisole (3,5-DFA) have been studied by gas-phase electron diffraction, ab initio (HF and MP2), and density functional theory (B3LYP) calculations. Both molecules have a planar heavy atom skeleton. 3,5-DFA exists as a single conformer of Cs symmetry, whereas 3-FA exists as a mixture of two planar conformers of Cs symmetry with the syn form (the O–CH3 bond is oriented toward the fluorine atom) being 0.1–0.2 kcal/mol lower in energy than the anti form (the O–CH3 bond is oriented away from the fluorine atom). From the experimental scattering intensities the following geometric parameters (ra distances and ∠α angles with 3σ uncertainties) were derived for 3,5-DFA: r(C–C)av=1.391(2) A, r(CPh–O)=1.359(13) A, r(CMe–O)=1.427(19) A, r(C–F)av=1.350(6) A, ∠C–C–C=116.0–123.6°, ∠C–O–C=118.7(12)°, ∠C2–C1–O=114.9(10)°, ∠C6–C1–O=124.9(10)°, ∠(C–C–F)av=118.4(17)°, and for 3-FA, syn conformer: r(C–C)av=1.393(3) A, r(CPh–O)=1.364(13) A, r(CMe–O)=1.423(14) A, r(C–F)=1.348(9) A, ∠C–C–C=117.7–123.1°, ∠C–O–C=118.4(11)°, ∠C2–C1–O=124.7(17)°, ∠C6–C1–O=115.1(17)°, ∠C2–C3–F=118.0(24)°. The mole fractions of the syn and anti conformers were found to be 0.55(17) and 0.45, respectively, in good agreement with the theoretical prediction. Ideal gas thermodynamic functions, S°(T), C p ° ( T ) , H°(T)−H°(0), for anisole, 3-FA, and 3,5-DFA were obtained on the basis of B3LYP calculations. Enthalpies of formations, Δf H 298 ° , were calculated using a Gaussian-3X (G3X) method and the method of isodesmic reactions. Calculated values of C p ° ( T ) and Δf H 298 ° for anisole are in good agreement with experimental data.

Density functional theory calculations on the tautomeric and conformational equilibria of 2-(2′-hydroxybenzoyl)pyrrole (HBP) and 2-(2′-methoxybenzoyl)pyrrole (MBP) were performed. Moreover, the experimental IR and UV spectra of the same compounds were recorded and compared with the theoretical data. The presence of an intramolecular hydrogen bond in HBP can be related to the biological activities of some of its derivatives.