Trends In Binding Energies Research Articles

Novel composite structures based on cobalt phthalocyanine/graphene oxide: Identification of potential drug candidates to treat Alzheimer’s disease and diabetes

This study produced novel cobalt phthalocyanine (CoPc) (2) and its graphene oxide (GO) composites (2a-2f) and examined their impact on several metabolic enzymes, including α-glycosidase (α-Gly), achetylcholinesterase (AChE) and butyrylcholinesterase (BChE). IC50 values showed that when compared to conventional inhibitors, all the compounds demonstrated strong inhibitory effects against all targets. The ranges for the Ki values of the compounds containing the AChE, BChE, and α-glycosidase enzymes were 26.15 ± 3.85–48.26 ± 7.43, 5.46 ± 0.57–10.68 ± 0.78, and 2.20 ± 0.11–22.41 ± 2.60 nM, in that order. In addition, pharmacodynamic studies, the model form of new CoPc/GO composites, their structural orientations in the active sites of AChE, BChE and α-Gly enzymes, respectively, their binding interaction mechanism, and even their drug potential were investigated. The relevant compound (CoPc/GO) shows a binding energy trend of −12.40, −12.30 and −12.10 kcal/mol to α-Gly, AChE and BChE enzymes, respectively. In addition, it was determined that the compounds exhibited cytotoxic effects against human breast cancer cells. After more than 20 years of usage, cholinesterase inhibitors (ChEIs) are still a crucial component of the therapy of Alzheimer’s disease (AD). In multiple multicenter, well-controlled trials, only ChEIs have consistently demonstrated efficacy against AD; as a result, they have been widely approved by national regulatory authorities. Even if there have been a lot of ChEI discoveries recently, drug discovery is a continuous process that involves looking for novel strategies and chemotypes.

A Free Energy Decomposition Analysis: Insight into Binding Thermodynamics from Absolutely Localized Molecular Orbitals.

Traditional energy decomposition analysis (EDA) methods can provide an interpretive decomposition of non-covalent electronic binding energies. However, by definition, they neglect entropic effects and nuclear contributions to the enthalpy. With the objective of revealing the chemical origins of trends in free energies of binding, we introduce the concept of a Gibbs decomposition analysis (GDA) by coupling the absolutely localized molecular orbital treatment of electrons in non-covalent interactions with the simplest possible quantum rigid rotor-harmonic oscillator treatment of nuclear motion at finite temperature. The resulting pilot GDA is employed to decompose enthalpic and entropic contributions to the free energy of association of the water dimer, fluoride-water dimer, and water binding to an open metal site in the metal-organic framework Cu(I)-MFU-4l. The results show enthalpic trends that generally track the electronic binding energy and entropic trends that reveal the increasing price of loss of translational and rotational degrees freedom with temperature.

Application of molecular docking simulation to screening of metal–organic frameworks

Assessment of the affinity of a material to specific gas/ligand molecules and the corresponding binding mechanisms can facilitate screening of materials, reduce experimental costs and prompt material discovery and development. This task has been successfully performed using conventional molecular docking simulation (CMDS) for biomolecules. But the relevance of CMDS to material discovery has not been systematically assessed. Our comprehensive study using Molegro Virtual Docker (MVD) shows that CMDS does not give accurate binding energy and selectivity trends for gas adsorption onto metal–organic frameworks (MOFs). Also, it cannot precisely predict drug loading and release trends. However, CMDS can already describe well the binding mechanisms and the preference of MOFs towards a specific gas. Accordingly, we discuss the roots of the shortcomings of CMDS and suggest some modifications to develop a specialized docking software for non-biological materials.

COMPUTATIONAL DESIGNING OF DEFERIPRONE BASED NOVEL DRUGS AS EFFICIENT ANTI-PARKINSON AGENTS

Comprehensive and detailed density functional theory (DFT) computations are done herein at the M05-2X/6-31G(d) level of theory to scrutinize the interactions of Fe3+ ions with computationally designed deferiprone (DFP)-based novel complexing drugs. The thermodynamic properties of metal-deferiprone complexes were determined in water as solvent. The theoretical binding energy trend indicated that [Fe(DrugC)3] has the highest interaction affinity. Natural bond orbital (NBO) analysis was used to estimate and assess atomic natural charges, the charge transfer between metal ions with ligands (oxygen atoms), and the interaction energy (E(2)) levels. The determined value of E(2) (donor-acceptor interaction energy) for the [Fe(DrugC)3] complex was found to be greater than those of the other complexes. The understudy novel chelators were made to interact with graphidyne based nanosheet to understand their adsorption behavior. Interestingly, ?---CH interaction of the complexes with the nanosheet were found around (2.41-3.12A), which endorsed their good behavior. The quantum theory of atoms in molecules (QTAIM) analysis was used to establish the type of efficient interactions and bonding characteristics in water. On the basis of the QTAIM results, [Fe(DrugC)3] was found to have the strongest M-O bond. The M-O bonds in the compounds were non-covalent, whereas they were electrostatic or partially covalent in all other complexes.

Insights into Omicron's Low Fusogenicity through In Silico Molecular Studies on Spike-Furin Interactions.

The Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant and its subvariants have a unique set of mutations. Two of those mutations (N679 K and P681 H) reside close to the S1 /S2 furin cleavage site (FCS; 685-686). When these mutations reside together, they exert less-efficient membrane fusion than wild type and most other variants of concern such as the Delta variant. Here, we in silico targeted these mutations to find out which of the amino acids and interactions change plays the key role in fusion. To comprehend the epistatic effect of N679 K and P681 H mutations on the spike protein, we in silico constructed three types of spike protein sequences by changing the respective amino acids on 679 and 681 positions (P681 H, N679 K, K679 N-H681 P variants). We then analyzed the binding affinity of furin and spike (Furin-Wild, Furin-Omicron, Furin-P681 H, Furin-N679 K, and Furin-K679 N/H681 P) complexes. Omicron and P681 H variants showed a similar higher binding energy trend compared to the wild type and N679 K. The variation in hydrogen, hydrophobic, and salt bridge bonds between spike protein and furin provided an explanation for the observed low fusogenicity of Omicron. The fate of the epistasis in furin binding and possible cleavage depends on the efficient interaction between FCS in spike and furin catalytic triad, and in addition, the loss of the hydrogen bond between Arg 681 (spike) and Asn 295 (furin) along with inhibitor-like ineffective higher affinity plays an important role in the enzymatic activity.

Experimental and Theoretical Characterization of Rh Single Atoms Supported on γ-Al2O3 with Varying Hydroxyl Contents during NO Reduction by CO

Oxide-supported Rh catalysts are important components of commercial three-way catalysts for pollution abatement. Despite their universal application, many mysteries remain about the active structure of Rh on oxide supports as these materials often contain a mixture of nanoparticles and single-atom Rh species on the same support, even after aging. Probe molecule Fourier transform infrared (FTIR) spectroscopy in this work shows that atomically dispersed Rh on γ-Al2O3 prefer to strongly bind CO when exposed to NO and CO mixtures and that light-off of NO reduction occurs at temperatures similar to CO desorption, suggesting that the first and rate-determining step in NO–CO reactions may be the desorption of CO from single-atom Rh dicarbonyl complexes, Rh(CO)2. Two sets of symmetric and asymmetric stretching frequencies associated with distinct Rh(CO)2 species are observed in FTIR spectra at 2084/2010 and 2094/2020 cm–1. During temperature ramps, the latter pair of bands at 2094/2020 cm–1 converts to the 2084/2010 cm–1 bands at 463 K before all symmetric and asymmetric bands disappear at 573 K. Bands then appear in the range of 1975–1985 cm–1 associated with Rh monocarbonyl, Rh(CO), species upon the disappearance of the 2084/2010 cm–1 bands, suggesting that CO desorbs sequentially from Rh(CO)2 by forming Rh(CO) intermediates. Combined DFT and FTIR experiments suggest that local OH coverage on the γ-Al2O3 surface distinguishes the two Rh(CO)2 species: the higher frequency species resides on a less hydroxylated region and migrates to a more hydroxylated region at higher temperatures, causing the CO vibrational frequency to decrease by ∼10 cm–1. CO desorption occurs from this Rh(CO)2 structure with high local OH coverage, consistent with the DFT predicted trend of CO binding energies. Because of the coincidence of CO desorption with the light-off of NO reduction, local support hydroxylation of atomically dispersed Rh1/γ-Al2O3 catalysts likely affects both the Rh structure after CO desorption and the kinetics of NO reduction, studies of which are enabled by the Rh(CO)2 model developed here.

An Efficient Cyan Emission from Copper (II) Complexes with Mixed Organic Conjugate Ligands.

Copper (II) complexes containing mixed ligands were synthesized in dimethyl formamide (DMF). The intense cyan emission at an ambient temperature is observed for solid copper (II) complexes with salicylic acid and a 12% quantum yield with a fluorescent lifetime of approximately 10 ms. Hence, copper (II) complexes with salicylic acid are excellent candidates for photoactive materials. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) reveal that the divalent copper metal centers coordinate with the nitrogen and oxygen lone pairs of conjugate ligands. XPS binding energy trends for core electrons in lower-lying orbitals are similar for all three copper (II) complexes: nitrogen 1s and oxygen 1s binding energies increase relative to those for undiluted ligands, and copper 2p3/2 binding energies decrease relative to that for CuCl2. The thermal behavior of these copper complexes reveals that the thermal stability is characterized by the following pattern: Cu(1,10-phenanthroline)(salicylic acid) > Cu(1,10-phenanthroline)(2,2’-bipyridine) > Cu(1,10-phenanthroline)(1-benzylimidazole)2.

Benchmarking binding energy calculations for organic structure-directing agents in pure-silica zeolites.

Molecular modeling plays an important role in the discovery of organic structure-directing agents (OSDAs) for zeolites. By quantifying the intensity of host-guest interactions, it is possible to select cost-effective molecules that maximize binding toward a given zeolite framework. Over the last few decades, a variety of methods and levels of theory have been used to calculate these binding energies. Nevertheless, there is no consensus on the best calculation strategy for high-throughput virtual screening undertakings. In this work, we compare binding affinities from density functional theory (DFT) and Dreiding force field calculations for 272 zeolite-OSDA pairs obtained from static and time-averaged simulations. Enabled by automation software, we show that Dreiding binding energies from the frozen pose method correlate best with DFT energies. They are also less sensitive to the choice of initial lattice parameters and optimization algorithms, as well as less computationally expensive than their time-averaged counterparts. Furthermore, we demonstrate that a broader exploration of the conformation space from molecular dynamics simulations does not provide significant improvements in binding energy trends over the frozen pose method despite being orders of magnitude more expensive. The code and benchmark data are open-sourced and provide robust and computationally efficient guidelines to calculating binding energies in zeolite-OSDA pairs.

Interaction of Aromatic Molecules with Forsterite: Accuracy of the Periodic DFT-D4 Method.

Density functional theory (DFT) has provided deep atomic-level insights into the adsorption behavior of aromatic molecules on solid surfaces. However, modeling the surface phenomena of large molecules on mineral surfaces with accurate plane wave methods (PW) can be orders of magnitude more computationally expensive than localized atomic orbitals (LCAO) methods. In the present work, we propose a less costly approach based on the DFT-D4 method (PBE-D4), using LCAO, to study the interactions of aromatic molecules with the {010} forsterite (Mg2SiO4) surface for their relevance in astrochemistry. We studied the interaction of benzene with the pristine {010} forsterite surface and with transition-metal cations (Fe2+ and Ni2+) using PBE-D4 and a vdW-inclusive density functional (Dion, Rydberg, Schröder, Langreth, and Lundqvist (DRSLL)) with LCAO methods. PBE-D4 shows good agreement with coupled-cluster methods (CCSD(T)) for the binding energy trend of cation complexes and with PW methods for the binding energy of benzene on the forsterite surface with a difference of about 0.03 eV. The basis set superposition error (BSSE) correction is shown to be essential to ensure a correct estimation of the binding energies even when large basis sets are employed for single-point calculations of the optimized structures with smaller basis sets. We also studied the interaction of naphthalene and benzocoronene on pristine and transition-metal-doped {010} forsterite surfaces as a test case for PBE-D4. Yielding results that are in good agreement with the plane wave methods with a difference of about 0.02–0.17 eV, the PBE-D4 method is demonstrated to be effective in unraveling the binding structures and the energetic trends of aromatic molecules on pristine and transition-metal-doped forsterite mineral surfaces. Furthermore, PBE-D4 results are in good agreement with its predecessor PBE-D3(BJM) and with the vdW-inclusive density functionals, as long as transition metals are not involved. Hence, PBE-D4/CP-DZP has been proven to be a robust theory level to study the interaction of aromatic molecules on mineral surfaces.

The effect of hydrostatic pressure on binding energy and polaron effect of bound polaron in wurtzite AlyGa1−yN/AlxGa1−xN parabolic quantum well

The effect of hydrostatic pressure on binding energy and polaron effect of the bound polaron in a wurtzite Al[Formula: see text]Ga[Formula: see text]N/Al[Formula: see text]Ga[Formula: see text]N parabolic quantum well (QW) is studied using the Lee–Low–Pines intermediate coupling variational method in the paper. The numerical relationship of binding energy and polaron effect of the bound polaron are given as a functions of pressure [Formula: see text], composition [Formula: see text] and well width [Formula: see text]. In the theoretical calculations, the anisotropy of the electron effective band mass, the optical phonon frequency, the dielectric constant and other parameters in the system varying with the pressure [Formula: see text] and the coordinate [Formula: see text] are included. The electron–optical phonon interaction and the impurity center–optical phonon interaction are considered. The results show that hydrostatic pressure has a very obvious effect on binding energy and polaron effect of the bound polaron in the wurtzite Al[Formula: see text]Ga[Formula: see text]N/Al[Formula: see text]Ga[Formula: see text]N parabolic QW. For QWs with determined structural parameters, the contributions of the three branch of phonons, i.e., the confined (CF) phonon, half-space (HS) phonon and the interface (IF) phonon, to binding energy of the polaron increase with the increase of the pressure [Formula: see text], the CF phonons contribute the most. Under the condition of a certain well width and hydrostatic pressure, with the increase of the composition [Formula: see text], the ground state binding energy of the bound polaron in the wurtzite Al[Formula: see text]Ga[Formula: see text]N/Al[Formula: see text]Ga[Formula: see text]N parabolic QW increases, and the contribution of the IF phonon and HS phonons to the binding energy decreases, while the contribution of the CF phonons and the total contribution of all phonons increase significantly. In the wurtzite Al[Formula: see text]Ga[Formula: see text]N/Al[Formula: see text]Ga[Formula: see text]N parabolic QW, the ground state binding energy of the bound polaron decreases with the increase of the well width. The decrease rate is greater in the narrow well, and smaller in the wide well. The contribution of different branches of phonons to binding energy varies with the change of the well width. With the increase of the well width, the contribution of CF phonons to binding energy increases, the contribution of HS phonons to binding energy decreases, and the IF phonon contribution and the total phonon contribution first increase to the maximum value and then gradually decrease slightly. The changing trend of binding energy of bound polaron in the wurtzite Al[Formula: see text]Ga[Formula: see text]N/Al[Formula: see text]Ga[Formula: see text]N parabolic QW, of the contribution of different branch phonons to binding energy with the pressure [Formula: see text], composition [Formula: see text] and well width [Formula: see text] is similar to that of the GaN/Al[Formula: see text]Ga[Formula: see text]N square QW, but the change in the parabolic QW is more obvious.

Optical properties of core/shell spherical quantum dots**Project supported by the Natural Science Foundation of Inner Mongolia Autonomous Region, China (Grant Nos. 2019MS01006 and 2020MS01008), the Science Project of the Higher Education of Inner Mongolia Autonomous Region, China (Grant No. NJZY19047), the Doctoral Starting-up Foundation of Inner Mongolia Agricultural University, China (Grant No. BJ2013B-2), and the Grassland Talent Project, China.

In this study, the effects of quantum dot size on the binding energy, radiative lifetime, and optical absorption coefficient of exciton state in both GaN/AlxGa1−xN core/shell and AlxGa1−xN/GaN inverted core/shell quantum dot structures are studied. For the GaN/AlxGa1−xN core/shell structure, the variation trend of binding energy is the same as that of radiation lifetime, both of which increase first and then decrease with the increase of core size. For AlxGa1−xN/GaN inverted core/shell structure, the binding energy decreases first and then increases with core size increasing, and the trends of radiation lifetime varying with core size under different shell sizes are different. For both structures, when the photon energy is approximately equal to the binding energy, the peak value of the absorption coefficient appears, and there will be different peak shifts under different conditions.

A DFT study on the metal ion selectivity of deferiprone complexes

In this work, systematic density functional theory (DFT) calculations were performed to study the interactions of various metal ions (Al3+, Fe3+, Co2+, Ni2+, Cu2+, and Zn2+) and the clinically useful chelating agent called deferiprone (DFP) at the M05-2X/6-31G(d) level of theory. The thermodynamic parameters of metal-deferiprone complexes were determined in water. Based on the obtained data, the theoretical binding energy trend is as follows: Al3+ > Fe3+ > Cu2+ > Ni2+ > Co2+ > Zn2+, confirming that [Al(DFP)3] has the most interaction energy. Moreover, Natural bond orbital analysis was employed to determine and analyze the natural charges on different atoms and charge transfer between the metal ions and ligands (oxygen atoms) as well as the interaction energy (E(2)) values. The calculated value of ƩE(2) (donor-acceptor interaction energy) for [Al(DFP)3] complex is higher than other complexes, which is according to energy analysis. To confirm the type of effective interactions and bonding properties in the water, the quantum theory of atoms in molecules (QTAIM) analysis was applied. QTAIM analysis confirmed that the strongest M - O bond is found in the [Al(DFP)3] complex. The calculated topological properties at the bond critical points, such as the ratio of the kinetic energy density to the potential energy density, -G(r)/V(r), electronic energy density, H(r), confirm that M - O bonds in the Al-deferiprone complex are non-covalent, while in other complexes, they are electrostatic and partially covalent.

Composition-Dependent Oxygen Reduction Reaction Activity of Pt-Surfaced PtNi Dodecahedral Nanoframes

Pt-based bimetallic nanoframes have been demonstrated to have high activity for a number of electrocatalytic reactions. Their morphology, crystal facets, and compositions are important factors that regulate their catalytic activities. Herein, we synthesized a series of Pt-surfaced PtNi dodecahedral nanoframes with variable Pt/Ni ratios. The nanoframes were prepared by oxidative etching of presynthesized PtNi rhombic dodecahedron nanoparticles. The Pt ratio in the PtNi nanoframes have been tuned from 28% to 65% by changing the duration of oxidative etching. In terms of catalytic performance, the PtNi nanoframes display a volcano-type behavior in specific oxygen reduction reaction (ORR) activity as a function of Pt ratio with a maximum ORR specific activity of 1.9 mA cm–2 observed with 47% Pt. The mass activity of the particles ranges from 0.72 to 0.92 A mg–1, which significantly exceeds the mass activity of 0.19 A mg–1 measured for commercial Pt NP/C. Density functional theory calculations reveal that the Pt ratio underneath the Pt skin in the nanoframes affects the binding energy of oxygenate species and thus the ORR activity. The trend of OH binding energy versus PtNi composition from the computational results qualitatively agrees with the trend of ORR activity from the experiments.

Photoelectron spectroscopy of [Mo6X14]2- dianions (X = Cl-I).

Photoelectron spectroscopy and theoretical investigations have been performed to systematically probe the intrinsic electronic properties of [Mo6X14]2- (X = halogen). All three PE spectra of gaseous [Mo6X14]2- (X = Cl, Br, I) dianions, which were generated by electrospray ionization, exhibit multiple resolved peaks in the recorded binding energy range. Theoretical investigations on the orbital structure and charge distribution were performed to support interpretation of the observed spectra and were further extended onto [Mo6F14]2-, a dianion that was not available for the experimental study. The measured adiabatic (ADE) and vertical detachment energies (VDE) for X = Cl-I were well reproduced by density functional theory calculations (accuracy ∼0.1 eV). Corresponding ADE/VDE values for the dianions were found to be 1.48/2.13 (calc.) and 2.30/2.65, 2.30/2.62, and 2.20/2.42 eV (all expt.) for X = F, Cl, Br, and I, respectively, showing an interesting buckled trend of electron binding energy (EBE) along the halogen series, i.e., EBE (F) ≪ EBE (Cl) ∼ EBE (Br) > EBE (I). Molecular orbital analyses indicate different mixing of metal and halogen atomic orbitals, which is strongly dependent on the nature of X, and suggest that the most loosely bound electrons are detached mainly from the metal core for X = F and Cl, but from halide ligands for X = Br and I. The repulsive Coulomb barrier (RCB), estimated from the photon energy dependent spectra, decreases with increasing halogen size, from 1.8 eV for X = Cl to 1.6 eV for X = I. Electrostatic potential modeling confirms the experimental RCB values and predicts that the most favorable electron detaching pathway should lie via the face-bridging halide ligands.

Electro-optical properties of a pressure-induced g−SiC7 sheet from many-body perturbation theory

Alongside a vast number of two-dimensional (2D) materials, $g\text{\ensuremath{-}}{\mathrm{SiC}}_{7}$ siligraphene has already been introduced to the 2D nanomaterial family with extraordinary sunlight absorption. In this work, we exploit the concept of the in-plane biaxial strain-induced electro-optical engineering in siligraphene from ab initio many-body perturbation theory calculations (GW + Bethe-Salpeter equation). While the semiconductor nature of the system is robust for both tensile and compressive strains, the direct GW band gap of 1.35 eV is decreased (increased) linearly with tensile (compressive) strain. This is accompanied by a variation in the optical transitions. The tensile strain in $g\text{\ensuremath{-}}{\mathrm{SiC}}_{7}$ shifts the optical absorption peaks to the lower photon energies, the so-called red shift, whereas the compressive strain causes a shift to the higher frequencies, the so-called blue shift. Eventually, the exciton binding energy trend and the real-space exciton distribution for the bright bound state is studied with strain, resulting in a alteration of the spatial distribution radius of exciton wave functions from tensile to compressive. Our findings extend the logic applications of siligraphene in photovoltaic devices, especially in tailoring the power conversion efficiency of excitonic solar cells.

A Study of SnnAl Clusters by Density Functional Theory: Comparison with Their Anions and Cations

The atomic structures, stabilities, electronic structures, and magnetic moments of neutral and singly positively and negatively charged SnnAl (n = 1–10) clusters are calculated with B3LYP/SDD method in density functional theory. Detailed analyses are implemented to acquire the properties of SnnAl(0, ±1) clusters, such as relative stabilities, electronic properties, natural population analyses, and magnetic moments. The calculation results show that the ground‐state structures of Sn2Al, Sn7Al, and Sn8Al clusters are different from those of Sn3, Sn8, and Sn9 clusters, the variation trend of binding energies of Snn + 1 and SnnAl(0, ±1) coincides, and the small kinks are the same. It is found that the changing tendency of the vertical electron detachment energies (VDEs) of Snn + 1 and SnnAl(0, ±1) is almost consistent with that of the adiabatic electron affinities (AEAs), except Sn8Al. Furthermore, the adiabatic ionization potential energies (AIPs) of SnnAl and Snn + 1 clusters exhibit oscillatory behavior, but the variation trend of SnnAl is contrary to that of Snn + 1 from n = 1 to n = 7. The simulation results indicate that SnnAl− and SnnAl+ display a similarity in the magnetic moments, when n = 1, 3, 4, 5, 6, 7, and 9. The charges are transferred from Al to Sn in Sn1–4Al.

Physics-informed machine learning for inorganic scintillator discovery.

Applications of inorganic scintillators-activated with lanthanide dopants, such as Ce and Eu-are found in diverse fields. As a strict requirement to exhibit scintillation, the 4f ground state (with the electronic configuration of [Xe]4fn 5d0) and 5d1 lowest excited state (with the electronic configuration of [Xe]4fn-1 5d1) levels induced by the activator must lie within the host bandgap. Here we introduce a new machine learning (ML) based search strategy for high-throughput chemical space explorations to discover and design novel inorganic scintillators. Building upon well-known physics-based chemical trends for the host dependent electron binding energies within the 4f and 5d1 energy levels of lanthanide ions and available experimental data, the developed ML model-coupled with knowledge of the vacuum referred valence and conduction band edges computed from first principles-can rapidly and reliably estimate the relative positions of the activator's energy levels relative to the valence and conduction band edges of any given host chemistry. Using perovskite oxides and elpasolite halides as examples, the presented approach has been demonstrated to be able to (i) capture systematic chemical trends across host chemistries and (ii) effectively screen promising compounds in a high-throughput manner. While a number of other application-specific performance requirements need to be considered for a viable scintillator, the scheme developed here can be a practically useful tool to systematically down-select the most promising candidate materials in a first line of screening for a subsequent in-depth investigation.

Density functional theory and surface reactivity study of bimetallic AgnYm (n+m = 10) clusters

Density functional theory calculations have been performed on pure silver (Agn), yttrium (Ym) and bimetallic silver yttrium clusters AgnYm (n + m = 2–10) for reactivity descriptors in order to realize sites for nucleophilic and electrophilic attack. The reactivity descriptors of the clusters, studied as a function of cluster size and shape, reveal the presence of different type of reactive sites in a cluster. The size and shape of the pure silver, yttrium and bimetallic silver yttrium cluster (n = 2–10) strongly influences the number and position of active sites for an electrophilic and/or nucleophilic attack. The trends of reactivities through reactivity descriptors are confirmed through comparison with experimental data for CO binding with silver clusters. Moreover, the adsorption of CO on bimetallic silver yttrium clusters is also evaluated. The trends of binding energies support the reactivity descriptors values. Doping of pure cluster with the other element also influence the hardness, softness and chemical reactivity of the clusters. The softness increases as we increase the number of silver atoms in the cluster, whereas the hardness decreases. The chemical reactivity increases with silver doping whereas it decreases by increasing yttrium concentration. Silver atoms are nucleophilic in small clusters but changed to electrophilic in large clusters.

First-Principles Study of Alkoxides Adsorbed on Au(111) and Au(110) Surfaces: Assessing the Roles of Noncovalent Interactions and Molecular Structures in Catalysis

Microscopic understanding of molecular adsorption on catalytic surfaces is crucial for controlling the activity and selectivity of chemical reactions. However, for complex molecules, the adsorption process is very system-specific and there is a clear need to elaborate systematic understanding of important factors that determine catalytic functionality. Here, we investigate the binding of eight molecules, including seven alkoxides and one carboxylate, on the Au(111) and Au(110) surfaces. Our density-functional theory calculations including long-range van der Waals interactions demonstrate the significant role of these “weak” noncovalent forces on the adsorption structures, energetics, and relative adsorbate stabilities. Interestingly, the binding energy trends are insensitive to the surface structure. Instead, the adsorption stability depends strongly on the structural and chemical characteristics of the molecules: linear vs branching configurations, number of unsaturated C–C bonds, bidentate adsorption, a...

Chromium-vacancy clusters in dilute bcc Fe-Cr alloys: An ab initio study

Using an ab initio approach, we explore the stability of small vacancy and vacancy-chromium clusters in dilute body-centred cubic Fe-Cr alloys. To explain experimental observations described in C.D. Hardie et al., J. Nucl. Mater.439, 33 (2013) and showing the occurrence of Cr segregation in low-Cr alloys, we investigate if chromium can form stable bound configurations with vacancies in alloys with chromium concentration below the low-temperature chromium solubility limit of 10–11 at. %. We find that a single vacancy can attract up to four Cr atoms in the most energetically favourable cluster configuration. The magnetic origin of the binding energy trend is confirmed by a correlation between the average value of the magnetic moment of a Cr atom and the binding energy. Similar trends are also found for di-vacancy-Cr clusters, confirming that they likely also characterise larger systems not yet accessible to ab initio calculations. The ratio of the binding energy to the number of Cr atoms increased more than twice in the di-vacancy case in comparison with a single vacancy case. The binding energy of clusters containing single vacancy as well as di-vacancies can be well described by analytical expression that includes numbers of vacancy-vacancy, vacancy-Cr, and Cr-Cr pairs.