Ground-state Structure Research Articles

Experimental Demonstration and Density Functional Theory Mechanistic Analysis of Arene C-H Bond Oxidation and Product Protection by Osmium Tetroxide in a Strongly Basic/Nucleophilic Solvent.

Reactions that result in the oxy-functionalization of sp2 C-H bonds to give phenols are relatively rare. Here we report experiments and density functional theory (DFT) calculations that demonstrate selective C-H bond hydroxylation of nitroarenes to their corresponding mono-phenoxide as the exclusive product using OsO4 in a highly basic solvent mixture of water, hydroxide, and pyridine. DFT calculations using a mixed explicit/continuum solvent approach indicate that there is likely a mixture of OsO4-hydroxide/pyridine ground-state structures that have competitive reactivity and that the mechanism involves the nucleophilic addition of an anionic metal-oxo species to the arene followed by a hydride transfer process that is different from the standard [3 + 2] mechanism often invoked for the OsO4 oxidation of σ and π bonds. This work demonstrates the utility of using a strongly basic solvent for C-H bond oxidation reactions as this effectively converts any reactive phenolic product into the corresponding phenoxide, which is protected and essentially inert to further oxidation by the nucleophilic metal-oxo species.

Inverse design and high-throughput screening of TM-A (TM: Transition metal; A: O, S, Se) cathodes for chloride-ion batteries

Transition metal oxychlorides (TMOCl) are one of the most attractive cathode materials for chloride ion batteries (CIBs) due to their layered framework and high stability in organic electrolytes. However, the conversion reaction of TMOCl at low Cl− content is harmful to the cycle performance and energy density of CIBs. In order to eliminate the conversion reaction, high-throughput screening combined with an inverse design method is applied to search Cl-free layered materials among the TM-A (A = O, S, Se) compounds. After a comprehensive evaluation of layered characteristics, thermodynamic and dynamic stability, FeSe and its chloride FeSeCl are found to both have layered ground state structures. The stable Fe-Se framework prevents the material from decomposing or reconstructing during Cl− extraction. Compared to the reported TMOCl cathodes, the discharge process from FeSeCl to FeSe is a constant intercalation reaction, which leads to a flat voltage platform, high reaction reversibility, and low reaction energy barrier. The extended Se-4p orbital ensures excellent electronic conductivity. In addition, the spacious Cl− channels in FeSeCl and FeSe result in low Cl− diffusion barriers of 0.28 and 0.13 eV, respectively, which is significantly improved compared to the reported TMOCl materials.

Prediction of Ground State Structures and Robust Weyl Fermionic States in MnRhP

Prediction of Ground State Structures and Robust Weyl Fermionic States in MnRhP

Structural evolution and electronic properties of pure and semiconductor atom doped in clusters: Inn - , Inn Si- , and Inn Ge- (n= 3-16).

The bonding and electronic properties of Inn - , Inn Si- , and Inn Ge- (n=3-16) clusters have been computationally investigated. An intensive global search for the ground-state structures of these clusters were conducted using the genetic algorithm coupled with density functional theory (DFT). The ground-state structures of these clusters have been identified through the comparison between simulated photoelectron spectra (PES) of the found lowest-energy isomers and the experimentally measured ones. Doping semiconductor atom (Si or Ge) can significantly change the structures of the In clusters in most sizes, and the dopant prefers to be surrounded by In atoms. There are three structural motifs for Inn X- (X=Si, Ge, n=3-16), and the transition occurs at sizes n=5 and 13. All Inn Si- and Inn Ge- share the same configurations and similar electronic properties except for n=8. Among all above studied clusters, In13 - stands out with the largest vertical detachment energy (VDE), HOMO-LUMO gap, (Eb ) and second order energy difference Δ2 E due to its closed electronic shell of (1S)2 (1P)6 (1D)10 (2S)2 (1F)14 (2P)6 . Similarly, the neutral In12 X (X=Si, Ge) clusters are also identified as superatoms but with electronic configuration of (1S)2 (1P)6 (2S)2 (1D)10 (1F)14 (2P)6 .

Magnetic complexity, magnetodielectric effect and DFT calculations on correlation driven Gd2CoMnO6 insulator

In the family of Re2CoMnO6 manganite double perovskites, in contrast to parent La2CoMnO6 compound, Gd2CoMnO6 exhibits multiple magnetic transitions; ferromagnetic (FM) ordering, TC ∼ 112 K followed by AFM transition, TN ∼ 47 K, Gd spins ordering for T < 10 K and large isothermal entropy changes. A study of DC field-superimposed AC magnetic susceptibility measurements revealed the field-induced magnetic glassy behavior below TC and enhancement of FM correlations above TC. From the analysis of Almeida-Thouless behavior and dynamical power-law fit to frequency dependent AC susceptibility, Gd2CoMnO6 exhibits a volume spin glass-like nature below the freezing temperature, Tf ∼ 117.5 K. The isothermal field-dependent magnetic and dielectric permittivity data and temperature dependent Raman measurements (reported in ref. R. X. Silvaet al., J, Appl. Phys. 114 194,102 (2013)) confirms the spin-phonon coupling induced magnetodielectric effect. Further, the ground-state electronic structure and magnetic properties of Gd2CoMnO6 are investigated using DFT + U formalism with Vienna Ab-initio Simulation Package (VASP) code and predicted the material to be a correlation-driven insulator. The correlation value of the Hubbard U parameter at the 4f-Gd elements changes the stability of the magnetic state from Ferri to FM spin alignment for Ueff ≥ 3 eV and is correlated to the experimentally observed field-induced transformation of the short-range-order FiM/spin-glass-like phase into the long-range ordered FM phase.

Time-dependent optimized coupled-cluster method with doubles and perturbative triples for first principles simulation of multielectron dynamics.

We report the formulation of a new, cost-effective approximation method in the time-dependent optimized coupled-cluster (TD-OCC) framework [T. Sato et al., J. Chem. Phys. 148, 051101 (2018)] for first-principles simulations of multielectron dynamics in an intense laser field. The method, designated as TD-OCCD(T), is a time-dependent, orbital-optimized extension of the “gold-standard” CCSD(T) method in the ground-state electronic structure theory. The equations of motion for the orbital functions and the coupled-cluster amplitudes are derived based on the real-valued time-dependent variational principle using the fourth-order Lagrangian. The TD-OCCD(T) is size extensive and gauge invariant, and scales as O(N 7) with respect to the number of active orbitals N. The pilot application of the TD-OCCD(T) method to the strong-field ionization and high-order harmonic generation from a Kr atom is reported in comparison with the results of the previously developed methods, such as the time-dependent complete-active-space self-consistent field (TD-CASSCF), TD-OCC with double and triple excitations (TD-OCCDT), TD-OCC with double excitations (TD-OCCD), and the time-dependent Hartree-Fock (TDHF) methods.

Modulating the ESIPT dynamics of 3HF derivatives via substitution and solvent effect: A theoretical study

The ground-state and excited-state electronic structure, electronic properties, vertical excitation and emission energies, as well as the potential energy curve of the excite-state intramolecular proton transfer (ESIPT) process for 3-hydroxyflavone (3HF) derivatives 2-(4-(diphenylamine)phenyl)-3-hydroxy-4H-chromen-4-one (PPC), 2-(4-(diethylamino)phenyl)-3-hydroxy-4H-chromen-4-one (EPC) and 2-(4-methoxyl)-3-hydroxy-4H-chromen-4-one (MNC) have been examined with DFT and TDDFT methods. We found that the ESIPT dynamics could be controlled via both the solvent effect and the substituents. Structurally and electronically, the strength of excited-state intramolecular hydrogen bond and the twisted intramolecular charge transfer degree could be tuned by changing the electron donating ability of the substituent, which in turn influences the ESIPT energy barrier. In particularly, the stronger the electron donating ability, the longer the excited-state hydrogen bond distance, accompanied by more twisted intramolecular charge transfer, and the higher energy barrier for ESIPT. Besides, we found that the emission energies for the derivatives are very sensitive to the excited-state intramolecular charge transfer degree, with PPC exhibiting the smallest emission energies, followed by EPC and MNC, which is consistent with experimental observations. Furthermore, the ESIPT energy barrier of 3HF derivatives in solvent increases when the solvent becomes more polar. This work provides significant insight into tuning the ESIPT dynamics in 3HF derivatives which is useful for the design of new organic fluorescent probes with excellent performance.

Design, synthesis and spectroscopic and structural characterization of novel N-(2-hydroxy-5-methylphenyl)-2,3-dimethoxybenzamide: DFT, Hirshfeld surface analysis, antimicrobial activity, molecular docking and toxicology.

The novel compound N-(2-hydroxy-5-methylphenyl)-2,3-dimethoxybenzamide, C16H17NO4, I, was prepared by a two-step reaction and then characterized by elemental analysis and X-ray diffraction (XRD) methods. Moreover, its spectroscopic properties were investigated by FT-IR and 1H and 13C NMR. Compound I crystallized in the monoclinic space group P21/c and the molecular geometry is not planar, being divided into three planar regions. Supramolecular structures are formed by connecting units via hydrogen bonds. The ground-state molecular structure of I was optimized by the DFT-B3LYP/6-31G(d,p) method and the theoretical structure was compared with that obtained by X-ray diffraction. Intermolecular interactions in the crystal network were studied by two-dimensional (2D) and three-dimensional (3D) Hirshfeld analyses. The calculated electronic transition results were examined and the molecular electrostatic potentials (MEPs) were also determined. The in vitro antimicrobial activities of I against three Gram-positive bacteria, three Gram-negative bacteria and two fungi were determined. The compound was compared with several control drugs and showed better activity than the amoxicillin standard against Gram-positive bacteria B. subtilis, S. aureus and E. faecalis, and Gram-negative bacteria E. coli, K. pneumoniae and P. aeruginosa. The density functional theory (DFT)-optimized structure of the small molecule was used to perform molecular docking studies with proteins from experimentally studied bacterial and fungal organisms using AutoDock to determine the most preferred binding mode of the ligand within the protein cavity. A druglikeness assay and ADME (absorption, distribution, metabolism and excretion) and toxicology studies were carried out and predict a good drug-like character.

Hydrogen evolution reactions between small-sized GanM (M = Ga, Al; n = 0, 1, 2, 3) clusters and water molecules

The reaction mechanism of the hydrogen evolution reaction (HER) between small GanM (M = Ga, Al; n = 0, 1, 2, 3) clusters and water molecules has been systematically studied. The ground state structures of GanM clusters and GanM@H2O (M = Ga, Al; n = 0, 1, 2, 3) complexes and the reactions pathway of GanM@H2O are predicted. Our research results show that the Gan + H2O (n = 1, 2, 3, 4) and Al + H2O reactions are all endothermic reactions, while the GanAl + H2O (n = 1, 2, 3) reactions are all exothermic reactions. Ga3Al + H2O reaction has the most excellent performed in GanM + H2O (M = Ga, Al; n = 0, 1, 2, 3) reactions. To further understand the reaction mechanism of Ga3Al + H2O reaction, the electronic structure of reactant and product of the Ga3Al + H2O are analyzed by NBO analysis method, and the DOS diagram of the product is drawn. Our research results provide a deeper molecular understanding of the chemical reaction of Ga, which may help to develop more efficient Ga doped and Ga-based catalysts.

The impact of optical excitation on the binding in complexes of the cationic gold dimer: Au2+N2${\rm{Au}_{2}^{+}} {\rm{N}_{2}} $ and Au2+N2O${\rm{Au}_{2}^{+}} {\rm{N}_{2}{\rm{O}}} $

AbstractThe vibrationally resolved Ã2Σ+ ← Σ+ transitions of and are reported together with a detailed characterization of important geometric and electronic properties, enabling a deep understanding of the bonding mechanism at the molecular level. Comparison with time‐dependent density functional theory calculations reveals that the ligand stabilizes the entity in the Σ+ state by donating electron density into the half‐filled bonding orbital leading to the strengthening of the , , and bonds. This effect is reversed in the Ã2Σ+ state, where the bonding orbital is already filled and the ligand destabilizes the bond by donating into the antibonding orbitals of . The spectral detail obtained provides a deep understanding of the interplay of multiple electronic states in gas‐phase metal‐complex cations, opening the door for a systematic approach in the study of excited state reactivity in organometallic chemistry.Key points High‐resolution spectroscopic characterization of complexes by photodissociation of mass‐selected ions in the optical range and determination of fundamental molecular constants and ligand binding energies Detailed insight into geometric and electronic structure of ground and excited state of catalytically relevant gold cluster cations Effect of ligands on chemical bonding and reactivity of in ground and excited electronic state

Stability and electronic properties of five new ternary tantalum carbonitrides

The crystal structures, mechanical properties, and electronic structures of tantalum carbonitride TaxCyNz have been predicted via crystal structure search combined with the first-principles calculations. Ground-state structures of five stoichiometric TaxCyNz (Ta2CN, Ta3C2N, Ta3CN2, Ta4C3N, and Ta4CN3) were first uncovered, and their stabilities were confirmed by the elastic constants and phonon dispersions calculations. The mechanical properties of these five new phases were then systematically studied. The hardness calculations suggested that Ta4C3N possesses the largest hardness (which reaches a value up to 25.8 GPa) among these five compositions. The metallic nature and the atomic bonding behavior were evaluated based on the electronic structures. Furthermore, thermodynamic assessment established that these designed phases can be synthesized at readily attainable pressures.

Structural and electrocatalytic properties of copper clusters: A study via deep learning and first principles

Determining the atomic structure of clusters has been a long-term challenge in theoretical calculations due to the high computational cost of density-functional theory (DFT). Deep learning potential (DP), as an alternative way, has been demonstrated to be able to conduct cluster simulations with close-to DFT accuracy but at a much lower computational cost. In this work, we update 34 structures of the 41 Cu clusters with atomic numbers ranging from 10 to 50 by combining global optimization and the DP model. The calculations show that the configuration of small Cun clusters (n = 10–15) tends to be oblate and it gradually transforms into a cage-like configuration as the size increases (n &amp;gt; 15). Based on the updated structures, their relative stability and electronic properties are extensively studied. In addition, we select three different clusters (Cu13, Cu38, and Cu49) to study their electrocatalytic ability of CO2 reduction. The simulation indicates that the main product is CO for these three clusters, while the selectivity of hydrocarbons is inhibited. This work is expected to clarify the ground-state structures and fundamental properties of Cun clusters, and to guide experiments for the design of Cu-based catalysts.

Theoretical prediction for growth behavior and electronic properties of monoanionic Ru2Gen− (n = 3–20) clusters

We present a detailed theoretical study on the structural and electronic properties of monoanionic Ru2Gen− (n = 3–20) clusters using comprehensive genetic algorithm combined with density functional theory (CGA-DFT). It is shown that the geometrical growth patterns of the ground state Ru2Gen− clusters are polyhedral pyramidal structures with n ≤ 9 and gradually to form pentagonal prism-based structures with two endohedral Ru atoms from 10 ≤ n ≤ 15, then the structures evolve into a oblate cage-like configuration with two Ru atoms in center from cluster sizes n ≥ 16. In general, one extra electron will influence the geometric structures of Ru2Gen clusters to compare with their neutral ones we have studied. Based on the obtained ground state structures, we find that the clusters of Ru2Ge10−, Ru2Ge12− and Ru2Ge14− have relatively higher structural and chemical stability in which Ru2Ge14− is more prominent through the analysis of binding energy, second order of energy difference and highest occupied and lowest unoccupied molecular orbital (HOMO-LUMO) gap. Furthermore, we analyzed natural charge, natural electronic configuration, the frontier molecular orbitals and orbital composition to verify the clusters of Ru2Gen− with n = 10, 12, 14 and 16 have relatively higher chemical stability owning to the less contribution of Ru-d orbitals. In addition, the clusters of Ru2Ge3−, Ru2Ge4−, Ru2Ge6−, Ru2Ge10− and Ru2Ge16− have magnetic moment of 3 μB, while others are 1 μB. And also the vertical detachment energy (VDE) and adiabatic detachment energy (ADE) for all ground state clusters are computed to support future experiment.

Multipartite entanglement in the random Ising chain

Quantifying entanglement of multiple subsystems is a challenging open problem in interacting quantum systems. Here, we focus on two subsystems of length $\ensuremath{\ell}$ separated by a distance $r=\ensuremath{\alpha}\ensuremath{\ell}$ and quantify their entanglement negativity ($\mathcal{E}$) and mutual information ($\mathcal{I}$) in critical random Ising chains. We find universal constant $\mathcal{E}(\ensuremath{\alpha})$ and $\mathcal{I}(\ensuremath{\alpha})$ over any distances, using the asymptotically exact strong disorder renormalization group method. Our results are qualitatively different from both those in the clean Ising model and random spin chains of a singlet ground state, like the spin-$\frac{1}{2}$ random Heisenberg chain and the random XX chain. While for random singlet states $\mathcal{I}(\ensuremath{\alpha})/\mathcal{E}(\ensuremath{\alpha})=2$, in the random Ising chain this universal ratio is strongly $\ensuremath{\alpha}$ dependent. This deviation between systems contrasts with the behavior of the entanglement entropy of a single subsystem, for which the various random critical chains and clean models give the same qualitative behavior. The reason is that $\mathcal{E}$ and $\mathcal{I}$ are sensitive to higher order correlations in the ground-state structure. Therefore, studying multipartite entanglement provides additional universal information in random quantum systems, beyond what we can learn from a single subsystem.

Ground-state structure, orbital ordering and metal-insulator transition in double-perovskite PrBaMn2O6

In recent years, A-site ordered half-doped double-perovskite manganites $\rm RBaMn_2O_6$ (R=rare earth) have attracted much attention due to their remarkable physical properties and a prospect of application as magnetoresistance, multiferroic, and oxygen storage materials. The nature of the ground state in ${\rm RBaMn_2O_6}$ as well as sequence of phase transitions taking place at cooling are not yet well understood due to complexity in both experimental and theoretical studies. Here we address the origin of the ground-state structure in PrBaMn$_2$O$_6$ as well as its electronic and magnetic properties. Utilizing GGA+U approach and specially designed strategy to perform structural optimization, we show that the system has two competing AFM-A and AFM-CE magnetic structures with very close energies. The AFM-A structure is a metal, while AFM-CE is an insulator and the transition to the insulating state is accompanied by the charge Mn$^{3+}$/Mn$^{4+}$, and orbital $3x^2-r^2$/$3y^2-r^2$ orderings. This orbital ordering results in strong cooperative Jahn-Teller (JT) distortions, which lower the crystal symmetry. Our findings give a key to understanding contradictions in available experimental data on ${\rm PrBaMn_2O_6}$ and opens up the prospects to theoretical refinements of ground-state structures in other ${\rm RBaMn_2O_6}$ compounds.

Macroscopic–microscopic calculations of the ground state properties of Z = 120 isotopes and their α-decay chains

One of the substantial successes achieved in nuclear physics in the last two decades was the synthesis of dozens of isotopes of new elements up to [Formula: see text]Og, which closed the seventh row of the periodic table and inspired the ambition of adding more elements. This work aims to study extensively the ground state structure and decay properties of proposed [Formula: see text] isotopes. We employed Macroscopic–microscopic scheme based on the Skyrme energy density functional, the Woods–Saxon single-particle potential and Strutinsky’s method to find the structure properties, in a multidimensional deformation space. The same nucleon–nucleon potential is used to find the [Formula: see text]-decay half-life, within the Preformed Cluster Model. For 45 [Formula: see text]120 isotopes, the total energy surfaces, ground state masses, binding energy, deformations and fissionability are determined. The [Formula: see text]-values of the different competing decays and [Formula: see text]-decay half-lives are investigated based on the obtained structure. The results indicate the [Formula: see text]120 isotopes to be the most bound among the studied isotopes. The smallest fission barriers are indicated for the [Formula: see text]120 isotopes. The [Formula: see text]120 isotopes showed the longer half-lives against [Formula: see text]-decay, with an order of [Formula: see text]. The longest half-lives are estimated for the [Formula: see text]120 ([Formula: see text] and [Formula: see text]120 ([Formula: see text] isotopes. The longest full decay chain ending with the stable [Formula: see text]Pb nucleus is anticipated for the [Formula: see text]120 isotope. The shortest decay chain of [Formula: see text]120 terminates after three [Formula: see text]-decays by the spontaneous fission of [Formula: see text]Fl.

Antimony nitride discovered by theoretical structure prediction, rapid thermal annealing, and in situ X-ray diffraction

Nitride materials have promising properties for optoelectronics, but synthesis is challenging because of their metastable character. Therefore, even some simple binary nitrides have not been reported, and their properties remain unknown. Here, we report a metastable Sb–N phase. Unconstrained first-principle crystal-structure predictions suggest that a semiconducting layered SbN phase could be synthesized under activated nitrogen conditions. Experimentally, we approach the synthesis by rapid thermal annealing of an amorphous thin-film precursor. In situ X-ray diffraction monitoring reveals a transient phase appearing at 500°C and lasting for 17 s. With molecular dynamics simulations, we conclude that the phase observed is related to the predicted ground-state structure but that it contains stacking variations. This research highlights the synergy between computational materials discovery and in situ structural characterization during synthesis and processing, enabling the identification and synthesizability of new materials at the frontier of thermodynamically metastable regions.

Microwave-assisted synthesis, characterizations, antimicrobial activities, and DFT studies on some pyridine derived Schiff bases

This study reports a joint experimental, theoretical and microbiological investigation on the (E)-N,N-dimethyl-4-((pyridine-2-ylmethylene)amino)aniline (5), (E)-N,N-dimethyl-4-((pyridine-4-ylmethylene)amino)aniline (6) and (E)-N,N-dimethyl-4-((pyridine-3-ylmethylene)amino)aniline (7). These compounds were synthesized with microwave method and their structures characterized by FT-IR, 1H-NMR, 13C-NMR, and elemental analysis tecniques. In the theoretical studies, torsional barriers analysis, ground state structure, Fourier Transform Infrared spectra (FT-IR), and Nuclear Magnetic Resonance spectra (NMR) of 5, 6, and, 7 were calculated by Density Functional Theory (DFT) computations. The conformers obtained from the torsional barrier scanning were optimized by B3LYP/6-31G(d,p) level. The harmonic vibrational frequencies, potential energy distribution (PED), infrared intensities, and NMR chemical shifts of the most stable conformers were determined using the B3LYP/6-311++G(d,p). Theoretically, predicted spectral data were compared with experimental results. Antimicrobial studies of the synthesized compounds were performed against various microbial strains. Antimicrobial activities of 5, 6, and, 7 were tested against selected bacteria and yeast through minimum inhibitory concentration (MIC) and diffusion method. Compound 7 was found to be the most active against bacteria and yeast, while compound 5 was found to be moderately active. Compounds 6 (against S. aureus and C. albicans) and, 7 were found to have a very high minimum inhibitory concentration, ranging between 1.95 and 7.81 g/mL (against P. aeruginosa and E. coli). Compounds (6 and 7) showed zone of inhibition values in the range of 10–20 mm against other bacteria except L. monocytogenes and S. thyphimurium.

Identifying Photocatalytic Active Sites of C2H6 C-H Bond Activation on TiO2 via Combining First-Principles Ground-State and Excited-State Electronic Structure Calculations.

The activation of C-H bonds at low temperatures has attracted widespread interest in heterogeneous catalysis, which involves complex thermocatalytic and photocatalytic reaction processes. Herein, we systematically investigate the photothermal catalytic process of C-H bond activation in C2H6 dehydrogenation on rutile TiO2(110). We demonstrate that the photochemical activity of the C2H6 molecule adsorbed on TiO2(110) is site-sensitive and that C2H6 is more easily adsorbed at the Ti5c site with a lower dehydrogenation energy barrier. The first C-H bond activation of the C2H6 adsorbed at the Ti5c site tends to occur in the ground state, whereas Obr-adsorbed C2H6 is more photoactive during the initial adsorption. During the dehydrogenation of C2H6, the photogenerated electrons are always located at the Ti4+ sites of the TiO2 substrate while the photogenerated holes can be captured by C2H6 to activate the C-H bond.

The simplest dense carbon allotrope: Ultra-hard body-centered tetragonal C4

From crystal chemistry rationale and geometry optimization onto ground state structures with DFT-based computations, a novel ultra-hard body-centered tetragonal C4 (tet-C4) is proposed as the simplest dense carbon allotrope. tet-C4 is identified as cohesive as diamond, and likewise built of corner sharing C4 tetrahedra in all directions. Qualified as mechanically stable from the elastic constants combinations, tet-C4 has Vickers hardness identical to that of both cubic and hexagonal (lonsdaleite) diamond. Dynamical stability of tet-C4 derived from all positive phonon bands also allows obtaining heat capacity close to the experimental data of diamond. The electronic band structure shows insulating tet-C4 with a large indirect band gap of 5 ​eV.