Ab Initio Analysis Research Articles

Electrolyte Composition Effects on the Formation of the Solid Electrolyte Interphases of Li-Metal Batteries: A Molecular Dynamics Study

We will present our recent effort to develop new materials for batteries using our nanobattery model able to simulate a much smaller battery containing all the main components of an actual size battery. We are testing Li-metal anodes with sulfur- and metal-oxide-based cathodes together with highly concentrated electrolytes as well as with localized highly concentrated electrolytes. Our approach consists on performing ab initio analysis and ab initio molecular dynamics simulations in order to determine energetics properties as well as reactive force fields to perform larger scale reactive molecular dynamics simulations that eventually will allow us to evaluate prospective battery systems based on cycling stability, formation of benign solid-electrolyte interphases, interfacial stability, ion-transport and its mechanisms, electron-transfer, output voltage, current and charge thresholds, battery capacity, ion-pairing, cluster and death lithium formation, dendrite growth, capacity fading. In the present work, we use molecular dynamics simulations to model a TMP-based electrolyte comprising TMP, lithium, and bis(fluorosulfonyl)imide (LiFSI) salt, exploring the effects of salt concentration on solvation and ion transport. A statistical analysis is performed to study ion pairing, clustering, mobility, and coordination of Li-ion with and without small amounts of diluent materials.

Validation of Ab-Initio-Predicted Magnetic Anisotropies and Magneto-structural Correlations in Linear Hetero-trinuclear DyIII -NiII 2 Compounds.

Reported are single crystal SQUID and single crystal high‐frequency/high‐field EPR data of a trinuclear complex with a rare six‐coordinate coordination sphere of a DyIII center coupled to two terminal six‐coordinate NiII ions. The analysis of the single crystal spectroscopic parameters allows for an accurate description of the ground state wavefunction. The experimental analysis is supplemented by the analysis of the paramagnetic NMR spectra, allowing for a thorough description of the DyIII center. The experimental data are interpreted on the basis of an ab initio ligand field analysis, and the computed parameters are in good agreement with the experimental observations. This supports the quality of the theoretical approach based on a pseudo‐spin Hamiltonian for the electronic ground state. Further support emerges from the ab initio ligand field theory based analysis of a structurally very similar system that, in contrast to the complex reported here, shows single molecule magnetic properties, and this is in agreement with the quantum‐chemical prediction and analysis.

Erosion of refractory carbides in high‐temperature hydrogen from ab initio computations

AbstractAdvanced concepts for in‐space propulsion require coatings that are resistant to erosion in high temperature and pressure hydrogen. The erosion of refractory carbides of interest for this application (ZrC, NbC, HfC, and TaC) is investigated using combined ab initio thermodynamic computations and equilibrium product analyses. The carbides are shown to erode through a combination of four governing reactions, the relative extent of which depend on environmental conditions. The product profiles from these reactions are complex but exhibit lower hydrogen saturation at higher temperatures and lower pressures. A metric is derived to determine the applicability of equilibrium analyses for erosion rates, based on experimental conditions. Heritage mass loss experiments on ZrC in hydrogen satisfy the equilibrium criteria, and, correspondingly, the computed equilibrium erosion rate agrees quantitatively. The results suggest that previously postulated non‐equilibrium effects, namely the prolonged incongruent vaporization originating from high carbon mobility, do not drive erosion over the hours‐long timescales of the experiments. For specific in‐space propulsion designs, comparisons of carbide performance show TaC and HfC outperform other carbides and meet the criteria needed to close designs.

Theoretical insights into tunable electronic and optical properties of Janus Al2SSe monolayer through strain and electric field

Motivated by the successful experimental fabrication of Janus structures recently, a systematic study of the structural, electronic, and optical properties of the Janus Al2SSe monolayer has been done through first-principles approach. Through phonon spectrum and ab initio molecular dynamics analysis, Al2SSe was confirmed to be dynamically and thermally stable. The Janus Al2SSe monolayer exhibits a semiconducting characteristics with indirect band gap of 2.079 eV at equilibrium. While biaxial strain can significantly alter band gap, the influence of electric field on electronic as well as optical properties is negligible. The optical absorbance of Al2SSe is activated in the visible light region and its intensity can be enhanced by strain. Our findings only highlight the physical properties but also provide an effective way for tuning the electronic and optical properties of Al2SSe monolayer by strain engineering.

Comment on “Distinction of Electron Dispersion in Time-Resolved Photoemission Spectroscopy”

In a recent paper [Phys. Rev. Lett. 125, 043201 (2020)] (Ref.1) Liao et al. propose a theory of the interferometric photoemission delay based on the concepts of the photoelectron phase and photoelectron effective mass. The present comment discusses the applicability and limitations of the proposed approach based on an ab initio analysis supported by vast literature. Two central assumptions of the paper are questioned, namely that the photoelectron can be characterized by a phase (have a well-defined phase velocity), and that it can always be ascribed an effective mass Theories based on these concepts are concluded to be inapplicable to real solids, which is illustrated by the example of the system addressed in Ref. 1. That the basic assumptions of the theory are never fulfilled in nature discredits the underlying idea of the "time-domain interferometric solid-state energy-momentum-dispersion imaging method" suggested in Ref. 1. Apart from providing a necessary caution to experimentalists, the present comment also gives an insight into the photoelectron wave function and points out problems and pitfalls inherent in modeling real crystals.

Ab Initio Analysis of Periodic Self-Assembly Phases of Borophene as Anode Material for Na-Ion Batteries

In this work, the use of periodic self-assembly phases of borophene as anode material for Na-ion batteries is carefully studied, by employing first-principle calculations. Na atom adsorptions on β1...

Elucidation of Molybdenum Trioxide Sulfurization: Mechanistic Insights into Two-Dimensional Molybdenum Disulfide Growth.

Powder vaporization is a common method for the generation of large-area, single-crystal, two-dimensional molybdenum disulfide. While commonly employed as a growth method, the fundamental molecular mechanisms are not well understood. Recent ab initio analyses have shown that molybdenum oxysulfide rings play a key role in the sulfurization of molybdenum trioxide from elemental sulfur. In this study, we utilize molecular dynamics simulations with a reactive force field and ab initio calculations to elucidate the reaction pathway of sulfur with molybdenum trioxide. The molecular dynamics simulations demonstrated that for all sulfur allotropes the reaction pathway could be reduced to that of disulfur, trisulfur, or a combination of the two and that molybdenum trioxide can catalyze the decomposition of larger sulfur allotropes. Ab initio calculations were used to illuminate the intermediates and transition states in the reaction pathways for disulfur and trisulfur. Analysis of the temperature dependence of the transition state energies shows that the maximum reaction rates occur between 1000 and 1100 K, which corresponds with commonly reported experimental growth temperatures for molybdenum disulfide.

PH DEPENDENT STRUCTURES OF BOVINE SERUM IN SOLUTION BY SMALL ANGLE NEUTRON SCATTERING

The pH-dependent structures of the bovine serum albumin (BSA), under physiological conditions that permit enzymatic activity, were investigated by small-angle neutron scattering (SANS). The unfolding behavior of BSA in solution is important to understand the mechanism of protein aggregation due to protein conformational change. The information of protein structure is crucial to design the perfect protein-based drug delivery device. This information will be useful as a complementary data of BSA crystal structure in static state. The structure of BSA in solution was found to be heart shaped, nearly identical to bovine serum albumin crystal structure. The globular heart shaped structure of BSA was still maintained at alkaline pH range of 7 to 11. It underwent partial unfolding at pH 5 and continued to unfold at pH 3. The unfolded-structure of BSA shows that the globular structure started to change into a cylinder-like structure at pH 3 which was clearly shown in Kratky plot. These results were confirmed with ab initio low-resolution shape calculation model analysis using GNOM and DAMMIF in obtaining the three-dimensional protein structure model.

Magnetism in Zigzag and Armchair CuO Nanoribbons: Ab Initio Analysis

The present work reports the magnetism analysis of zigzag and armchair forms of CuO nanoribbons by using density functional theory (DFT)-based ab initio approach. The structural stability has been confirmed through the binding energy calculation. The electronic and magnetic properties have been analyzed as a function of varied width of CuO nanoribbons, interesting information for variety of applications. The metallic and ferromagnetic behaviors of CuO nanoribbons are observed, whereas its bulk counterpart shows a p-type semiconducting and antiferromagnetic nature. The computed magnetic moments for the zigzag and armchair forms of CuO nanoribbon are in the ranges of 0.19–0.61 μB and 0.24–0.97 μB, respectively. The computed spin polarizations confirms the half or full metallic ferromagnetic nature of these nanoribbons.

Bovine serum albumin refolding at acid solution by small angle neutron scattering

A series of study of the conformational change of bovine serum albumin (BSA) induced by pH and additive has been conducted by small angle scattering (SANS) technique. The unfolding process occur by increasing the solvent acidity of the buffer. The previous work from SANS scattering profile shows that BSA unfolded into a cylinder-like structure at pH 2. In this work, the role of sorbitol in refolding process of BSA in acid solution was studied. Sorbitol, at concentrations from 0 to 3 M, led to the progressive restoration of BSA globular structure. The SANS scattering data show the conformational change from cylinder-like structure of pure BSA at pH 2 undergo to ellipsoid-like structure in the addition of 3M sorbitol. In the absence, 1M and 2M sorbitol, the SANS scattering profile of BSA fitted to flexible cylinder model. Meanwhile in the present of 3M sorbitol, it fitted to triaxial ellipsoid model. These results are confirmed with ab initio low-resolution shape calculation model analysis using GNOM and DAMMIN obtaining the three-dimensional structure model.

Daylight-White-Emitting and Abnormal Thermal Antiquenching Phosphors Based on a Layered Host SrIn2(P2O7)2.

Single-phase white-emission phosphors possess a judicious usage potential in phosphor-converted white-light-emitting diodes (WLEDs). Recently, numerous efforts have been made toward the development of new patterns of white-emitting phosphors that achieve excellent quantum yield, superior thermal stability, and applaudable cost effectiveness of WLEDs. Finding suitable single-component white phosphor hosts to provide an ideal local environment for activators remains urgent. Inspired by the original discovery of the promising host MgIn2(P2O7)2 (MIP) and its structural dependence on alkali-metal cations, we synthesized a brand-new phosphor host, SrIn2(P2O7)2 (SIP), via the traditional solid-state reaction. Its crystal structure was determined using an ab initio analysis and the Rietveld method. It belongs to a monoclinic unit cell with the space group C2/c. Besides, SIP exhibits a special layered three-dimensional framework in which the monolayer [SrO10]∞ was surrounded by a bilayer [In2P4O14]∞ made of the InO6 octahedra and P2O7 groups. A series of pure SIP:Tm3+,Dy3+ phosphors with tunable blue-white-yellow emission were prepared by adjusting the dopant concentration and utilizing the Tm3+-Dy3+ energy transfer. The daylight-white-emitting phosphor SIP:0.01Tm3+,0.04Dy3+ (the correlated color temperature is 4448 K) exhibits an abnormal thermal antiquenching property, and the emission intensity of 423 K reaches 103.7% of the initial value at 300 K. On the basis of the temperature-dependent lattice evolution and microenvironment analysis, the reduction of β and lattice distortion can lead to lower asymmetry of the activators and benefit the compensation of trapped-electron thermal activation. In this work, an integration study was carried out on the crystal structure of the new matrix, the occupation of the luminescent center, the interaction of different activators in the host, and the distortion degree of the local structure for the activators, which is of great practical sense for producing a novel single-matrix white phosphor possessing superior thermal endurance for UV-light-stimulated WLEDs.

A Local D4h Symmetric Dysprosium(III) Single-Molecule Magnet with an Energy Barrier Exceeding 2000 K*.

Three six-coordinate DyIII single-molecule magnets (SMMs) [Dy(Ot Bu)2 (L)4 ]+ with local D4h symmetry are obtained by optimizing the equatorial ligands. One of the compounds with L=4-phenylpyridine shows an energy barrier (Ueff ) of 2075(11) K, which is the third largest Ueff , and the first Ueff >2000 K for SMMs with axial-type symmetry so far. Ab initio analysis indicates that the exceptional uniaxial magnetic anisotropy is deeply related to the axially compressed octahedral geometry. This work provides a new insight into the local D4h symmetry for high-performance SMMs.

Transformation of Bulk Pd to Pd Cations in Small-Pore CHA Zeolites Facilitated by NO.

Atomic dispersion of metal species has attracted attention as a unique phenomenon that affects adsorption properties and catalytic activities and that can be used to design so-called single atom materials. In this work, we describe atomic dispersion of bulk Pd into small pores of CHA zeolites. Under 4% NO flow at 600 °C, bulk Pd metal on the outside of CHA zeolites effectively disperses, affording Pd2+ cations on Al sites with concomitant formation of N2O, as revealed by microscopic and spectroscopic characterizations combined with mass spectroscopy. In the present method, even commercially available submicrosized Pd black can be used as a Pd source, and importantly, 4.1 wt % of atomic Pd2+ cations, which is the highest loading amount reported so far, can be introduced into CHA zeolites. The structural evolution of bulk Pd metal is also investigated by in situ X-ray absorption spectroscopy (XAS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), as well as ab initio thermodynamic analysis using density functional theory (DFT) calculations.

Synthesis of a novel crystalline organic–inorganic hybrid material KCS-11, an ethanol-breathing pseudoporous layered aluminosilicate

A novel crystalline organic–inorganic hybrid aluminosilicate material was successfully synthesized using methyltrimethoxysilane as a silicon source. Ab initio crystal structure analysis using powder X-ray diffraction data elucidated that this material was composed of the ordered stacking of layered aluminosilicates similar to sodalite-type zeolites and that methyl groups bonded to silicon atoms were arrayed on the inner surface of the interlayer. This material selectively inhaled amphiphilic molecules such as alcohols to open its interlayer distance. It could even breathe ethanol vapor at quite a low pressure and extract ethanol from the aqueous solution.

Identification of 1,2,3-triazole-phthalimide derivatives as potential drugs against COVID-19: a virtual screening, docking and molecular dynamic study

In this work we aimed to perform an in silico predictive screening, docking and molecular dynamic study to identify 1,2,3-triazole-phthalimide derivatives as drug candidates against SARS-CoV-2. The in silico prediction of pharmacokinetic and toxicological properties of hundred one 1,2,3-triazole-phtalimide derivatives, obtained from SciFinder® library, were investigated. Compounds that did not show good gastrointestinal absorption, violated the Lipinski's rules, proved to be positive for the AMES test, and showed to be hepatotoxic or immunotoxic in our ADMET analysis, were filtered out of our study. The hit compounds were further subjected to molecular docking on SARS-CoV-2 target proteins. The ADMET analysis revealed that 43 derivatives violated the Lipinski’s rules and 51 other compounds showed to be positive for the toxicity test. Seven 1,2,3-triazole-phthalimide derivatives (A7, A8, B05, E35, E38, E39, and E40) were selected for molecular docking and MFCC—ab initio analysis. The results of molecular docking pointed the derivative E40 as a promising compound interacting with multiple target proteins of SARS-CoV-2. The complex E40-Mpro was found to have minimum binding energy of −10.26 kcal/mol and a general energy balance, calculated by the quantum mechanical analysis, of −8.63 eV. MD simulation and MMGBSA calculations confirmed that the derivatives E38 and E40 have high binding energies of −63.47 ± 3 and −63.31 ± 7 kcal/mol against SARS-CoV-2 main protease. In addition, the derivative E40 exhibited excellent interaction values and inhibitory potential against SAR-Cov-2 main protease and viral nucleocapsid proteins, suggesting this derivative as a potent antiviral for the treatment and/or prophylaxis of COVID-19. Communicated by Ramaswamy H. Sarma

The nature of the chemical bond in sodium tungstate based on ab initio, DFT and QTAIM topological analysis of electron density

Abstract In the present study, we carried out a detailed study of interactions in sodium tungstate dihydrate [Na2WO4·2H2O] using computational methods. The solid-state DFT calculations carried out on accurately re-determined crystal structure of sodium tungstate dihydrate using positional parameters obtained from single crystal diffraction experiment. The Energies of interatomic and intermolecular interactions, the hydrogen bonds in particular, are estimated as Eint ≈ −0.5Vb. The topological properties based on Bader’s theory of atoms in molecules using AIMALL program employed to evaluate the interaction energies. Also the parameters such as electron density (ρ), Laplacian (∇2ρ), local potential energy (Vb), and kinetic potential energy (Gb) at bond critical points were obtained for all the non-covalent interactions. Among the number of non-bonding Na…O ionic interactions, the hydrate mediated O–H…O hydrogen bond found to be stronger with interaction energy of 24.46 kJ/mol.

Solvent effect on the 195Pt NMR properties in pyridonate-bridged PtIII dinuclear complex derivatives investigated by ab initio molecular dynamics and localized orbital analysis.

An ab initio molecular dynamics investigation of the solvent effect (water) on the structural parameters, 195Pt NMR spin-spin coupling constants (SSCCs) and chemical shifts of a series of pyridonate-bridged PtIII dinuclear complexes is performed using Kohn-Sham (KS) Car-Parrinello molecular dynamics (CPMD) and relativistic hybrid KS NMR calculations. The indirect solvent effect (via structural changes) has a dramatic effect on the 1JPtPt SSCCs. The complexes exhibit a strong trans influence in solution, where the Pt-Pt bond lengthens with increasing axial ligand σ-donor strength. In the diaqua complex, where the solvent effect is more pronounced, the SSCCs averaged for CPMD configurations with explicit plus implicit solvation agree much better with the experimental data, while the calculations for static geometry and CPMD unsolvated configurations show large deviations with respect to experiment. The combination of CPMD with hybrid KS NMR calculations provides a much more realistic computational model that reproduces the large magnitudes of 1JPtPt and 195Pt chemical shifts. An analysis of 1JPtPt in terms of localized and canonical orbitals shows that the SSCCs are driven by changes in the s-character of the natural atomic orbitals of Pt atoms, which affect the 'Fermi contact' mechanism.

Interplay of Hückel and Möbius Aromaticity in Metal-Metal Quintuple Bonded Complexes of Cr, Mo, and W with Amidinate Ligand: Ab initio DFT and Multireference Analysis*.

The aromaticity of metal-metal quintuple bonded complexes of the type M2 L2 (M=Cr, Mo, and W; L=amidinate) are studied employing gauge including magnetically induced ring current (GIMIC) analysis and electron density of delocalized bonds (EDDB). It is found that the complexes possess two types of aromaticity: i) Hückel aromaticity through delocalization of ligand π electrons with metal-metal δ-bond-forming 6 conjugated electrons (4π and 2δ) ring; ii) Craig-Möbius aromaticity through delocalization of π electrons of both the ligands with metal d-orbitals in Craig type orientation forming 10π electrons ring with a double twist. Extended transition state natural orbital chemical valence (ETS-NOCV) and canonical molecular orbital natural chemical shielding (CMO-NCS) analysis confirm the Craig-Möbius type arrangement of the orbitals. Furthermore, the unprecedented Hückel and Möbius type aromaticity is confirmed from the plot of the current pathways using 3D line integral convolution (3D-LIC) plots. The metal-metal bond order also increases down the group as justified from the complete active space self-consistent field (CASSCF) analysis. Due to an increase in the π and δ electron conjugation, both the Hückel and Möbius aromaticity increase down the group.

Performance Analysis of Integrated Electro-Optic Phase Modulators Based on Emerging Materials

Electro-optic modulators are utilized ubiquitously ranging from applications in data communication to photonic neural networks. While tremendous progress has been made over the years, efficient phase-shifting modulators are challenged with fundamental tradeoffs, such as voltage-length, index change-losses or energy-bandwidth, and no single solution available checks all boxes. While voltage-driven phase modulators, such as based on lithium niobate, offer low loss and high speed operation, their footprint of 10’s of cm-scale is prohibitively large, especially for density-critical applications, for example in photonic neural networks. Ignoring modulators for quantum applications, where insertion loss is critical, in this work we distinguish between current versus voltage-driven modulators. We focus on the former, since current-based schemes of emerging thin electro-optical materials have shown unity-strong index modulation suitable for heterogeneous integration into foundry waveguides. Here, we provide an in-depth ab-initio analysis of obtainable modulator performance based on heterogeneously integrating low-dimensional materials, i.e., graphene, thin films of indium tin oxide, and transition metal dichalcogenide monolayers into a plurality of optical waveguide designs atop silicon photonics. Using the fundamental modulator tradeoff of energy-bandwidth-product as a design-quality quantifier, we show that a small modal cross section, such as given by plasmonic modes, enables high-performance operation, physically realized by arguments on charge-distribution and low electrical resistance. An in-depth design understanding of phase-modulator performance, beyond doped-junctions in silicon, offers opportunities for micrometer-compact yet energy-bandwidth-ratio constrained modulators with timely opportunities to hardware-accelerate applications beyond data communication towards photonic machine intelligence, for instance; where both performance and integration-density are critical.

Ultrafast spin-currents and charge conversion at 3d-5d interfaces probed by time-domain terahertz spectroscopy

Spintronic structures are extensively investigated for their spin–orbit torque properties, required for magnetic commutation functionalities. Current progress in these materials is dependent on the interface engineering for the optimization of spin transmission. Here, we advance the analysis of ultrafast spin-charge conversion phenomena at ferromagnetic-transition metal interfaces due to their inverse spin-Hall effect properties. In particular, the intrinsic inverse spin-Hall effect of Pt-based systems and extrinsic inverse spin-Hall effect of Au:W and Au:Ta in NiFe/Au:(W,Ta) bilayers are investigated. The spin-charge conversion is probed by complementary techniques—ultrafast THz time-domain spectroscopy in the dynamic regime for THz pulse emission and ferromagnetic resonance spin-pumping measurements in the GHz regime in the steady state—to determine the role played by the material properties, resistivities, spin transmission at metallic interfaces, and spin-flip rates. These measurements show the correspondence between the THz time-domain spectroscopy and ferromagnetic spin-pumping for the different set of samples in term of the spin mixing conductance. The latter quantity is a critical parameter, determining the strength of the THz emission from spintronic interfaces. This is further supported by ab initio calculations, simulations, and analysis of the spin-diffusion and spin-relaxation of carriers within the multilayers in the time domain, permitting one to determine the main trends and the role of spin transmission at interfaces. This work illustrates that time-domain spectroscopy for spin-based THz emission is a powerful technique to probe spin-dynamics at active spintronic interfaces and to extract key material properties for spin-charge conversion.