Local Structural Deformation Research Articles

Multivalent metal perovskite YbCoO3 as a novel proton-conducting electrolyte for solid oxide fuel cells

For solid oxide fuel cells, an electrolyte with good stability and high ion conductivity is highly desired but difficult to obtain. Recently, a novel hydrogenation mechanism other than water dissociation have been reported in multivalent metal-based oxides, which provide a new route to increase proton concentration as well as proton conductivity. In this computational study, we propose the multivalent metal perovskite YbCoO3 as a promising proton-conducting electrolyte due to its good thermodynamic and chemical stability, semiconductor characteristics, high-concentration proton incorporation, and low proton migration barrier. Our findings also reveal that charge compensation of the multivalent metal is crucial for the high-concentration proton incorporation. On the other hand, both the shortening of the O-O distance and the Co-H repulsion play key roles in determining the energy barrier to proton migration, where local structural deformations are responsible for facilitating intra- and inter-octahedron proton transfer in YbCoO3. Our results might assist in the development of high-performance proton-conducting electrolytes for advanced solid oxide fuel cells.

Suppressed nonradiative electron–hole recombination in bismuth halide perovskite Cs3Bi2Cl9: Time domain ab initio analysis

Time-domain density functional theory, coupled with non-adiabatic molecular dynamics simulations, was employed to explore the defect characteristics and the associated nonradiative recombination processes in the bismuth halide perovskite Cs3Bi2Cl9. Our findings indicate that Cs3Bi2Cl9 inherently exhibits p-type semiconductor behavior, with vacancies at the Cs and Bi sites acting as predominant shallow acceptor defects. Although Cl vacancy and interstitial Cl defects introduce trap states within the bandgap of Cs3Bi2Cl9, the by-defect electron–hole (e-h) recombination is substantially impeded, which is attributed to the remarkable local structural deformations associated with the BiCl63− octahedral compression around the defects, which further results in decoupling between the defect state and the band edge state. As a result, the enhanced delocalization of defect states leads to a notably small wave function overlap between defect states and band edge states, as well as weak nonadiabatic couplings dominated by low-frequency phonons. Our study offers crucial insights into the mechanism of defect-mediated e-h recombination in bismuth-based perovskites and provides guidelines for designing efficient optoelectronic devices based on these materials.

Nanoporosity changes of graphene oxide colloids on linkage-treatment with molecular linker and heating after the linkage-treating

This study examined the nanoporosity of graphene oxide (GO) and graphene colloids bridge-treated with amino linkers using comparative nanoporosimetry with N2 and Ar adsorption. The spectroscopic measurements revealed the linkage via amino linkers in the linkage-treated GO and graphene colloids. The linkage-treatment expanded the d-spacing of GO by 0.21 nm and the d-spacing of the linkage-treated GO colloid decreased from 1.01 to 0.35 nm upon heating. The linkage-treated graphene colloids exhibited significant adsorption and an adsorption hysteresis, regardless of the reduction of d-spacing. Heating of linkage bonds induced the local structural deformation, providing open pores and the assembled mesoscale structure.

Intrinsic Defect and Deformation on Local Structure Caused by Rare‐Earth Ions in the Na3V2(PO4)2F3 Cathode Material

Na3V2(PO4)2F3 has been attracting a lot of attention as a positive electrode material for sodium‐ion batteries (SIBs). The deformation of local structure caused by rare‐earth ions and intrinsic defect properties in Na3V2(PO4)2F3 as a positive electrode for SIB have been investigated with atomistic simulation based on the lattice energy minimization. A good reproduction of the Na3V2(PO4)2F3 structure is obtained. It is revealed that Na Frenkel defect, which is formed by sodium interstitial and vacancy pair, is the most favorable type of intrinsic defect. This leads to the formation of stable sodium vacancy required for the Na‐ion diffusion. The results indicate that trivalent rare‐earth dopants at the V3+ site are the most energetically favorable dopants for Na3V2(PO4)2F3, and that the incorporation at the Na and P site could be used as a strategy to increase the sodium vacancy and interstitial, respectively. The deformation in the local structure by the rare‐earth ions doping at the V site is also investigated as helpful in improving the rate performance of SIBs.

Inhibitory effect of acarbose on tyrosinase: application of molecular dynamics integrating inhibition kinetics

Due to its clinical and cosmetic applications, investigators have paid attention to tyrosinase (TYR) inhibitor development. In this study, a TYR inhibition study with acarbose was investigated to gain insights into the regulation of the catalytic function. Biochemical assay results indicated that acarbose was turned to be an inhibitor of TYR in a reversible binding manner and probed as a distinctive mixed-type inhibitor via measurement of double-reciprocal kinetic (K i = 18.70 ± 4.12 mM). Time-interval kinetic measurement indicated that TYR catalytic function was gradually inactivated by acarbose in a time-dependent behavior displaying with a monophase process that was evaluated by semi-logarithmic plotting. Spectrofluorimetric measurement by integrating with a hydrophobic residue detector (1-anilinonaphthalene-8-sulfonate) showed that the high dose of acarbose derived a conspicuous local structural deformation of the TYR catalytic site pocket. Computational docking simulation showed that acarbose bound to key residues such as HIS61, TYR65, ASN81, HIS244, and HIS259. Our study extends an understanding of the functional application of acarbose and proposes that acarbose is an alternative candidate drug for a whitening agent via direct retardation of TYR catalytic function and it would be applicable for the relevant skin hyperpigmentation disorders concerning the dermatologic clinical purpose. Communicated by Ramaswamy H. Sarma

Elucidation of pH-Induced Protein Structural Changes: A Combined 2D IR and Computational Approach.

The acid-base behavior of amino acids plays critical roles in several biochemical processes. Depending on the interactions with the protein environment, the pKa values of these amino acids shift from their respective solution values. As the side chains interact with the polypeptide backbone, a pH-induced change in the protonation state of aspartic and glutamic acids might significantly influence the structure and stability of a protein. In this work, we have combined two-dimensional infrared spectroscopy and molecular dynamics simulations to elucidate the pH-induced structural changes in an antimicrobial enzyme, lysozyme, over a wide range of pH. Simultaneous measurements of the carbonyl signals arising from the backbone and the acidic side chains provide detailed information about the pH dependence of the local and global structural features. An excellent agreement between the experimental and the computational results allowed us to obtain a residue-specific molecular understanding. Although lysozyme retains the helical structure for the entire pH range, one distinct loop region (residues 65-75) undergoes local structural deformation at low pH. Interestingly, combining our experiments and simulations, we have identified the aspartic acid residues in lysozyme, which are influenced the most/least by pH modulation.

Novel MRI deformation-heterogeneity radiomic features are associated with molecular subgroups and overall survival in pediatric medulloblastoma: Preliminary findings from a multi-institutional study.

Medulloblastoma (MB) is a malignant, heterogenous brain tumor. Advances in molecular profiling have led to identifying four molecular subgroups of MB (WNT, SHH, Group 3, Group 4), each with distinct clinical behaviors. We hypothesize that (1) aggressive MB tumors, growing heterogeneously, induce pronounced local structural deformations in the surrounding parenchyma, and (b) these local deformations as captured on Gadolinium (Gd)-enhanced-T1w MRI are independently associated with molecular subgroups, as well as overall survival in MB patients. In this work, a total of 88 MB studies from 2 institutions were analyzed. Following tumor delineation, Gd-T1w scan for every patient was registered to a normal age-specific T1w-MRI template via deformable registration. Following patient-atlas registration, local structural deformations in the brain parenchyma were obtained for every patient by computing statistics from deformation magnitudes obtained from every 5mm annular region, 0 < d < 60 mm, where d is the distance from the tumor infiltrating edge. Multi-class comparison via ANOVA yielded significant differences between deformation magnitudes obtained for Group 3, Group 4, and SHH molecular subgroups, observed up to 60-mm outside the tumor edge. Additionally, Kaplan-Meier survival analysis showed that the local deformation statistics, combined with the current clinical risk-stratification approaches (molecular subgroup information and Chang's classification), could identify significant differences between high-risk and low-risk survival groups, achieving better performance results than using any of these approaches individually. These preliminary findings suggest there exists significant association of our tumor-induced deformation descriptor with overall survival in MB, and that there could be an added value in using the proposed radiomic descriptor along with the current risk classification approaches, towards more reliable risk assessment in pediatric MB.

Super-resolved discrimination of nanoscale defects in low-dimensional materials by near-field photoluminescence spectral imaging

Low-dimensional materials (LDMs), such as monolayer transition-metal dichalcogenides, have emerged as candidate materials for next-generation optoelectronics devices. Detection of the spatial heterogeneity caused by various nanoscale defects in LDMs, is crucial for their applications. Here, we report the super-resolved discrimination of various nanoscale defects in LDMs by near-field photoluminescence (NFPL) spectral imaging of LDMs with scanning near-field optical microscopy. As a demonstration example, a monolayer WS2 sample is characterized with a sub-diffraction spatial resolution of 140 nm in ambient environment. By performing topography and NFPL mapping, different defects, such as the stacks, bubbles, and wrinkles, can be identified through their light emission properties, which strongly correlate with the exciton emission modulation and tensile strain arising from local structural deformations.

Tuning the electronic and magnetic properties of O Vacancy and nonmetallic atoms doped monolayer SnO: A first-principles study

Using first-principles calculations, we systematically investigate the geometric structure, electronic structure and magnetic properties of bulk and monolayer Tin monoxide (SnO), as well as the influence of O vacancy and non-metallic elements, including H, B, C, F, Si, P and S, on the stability, structure and magnetic properties of monolayer SnO. In this paper, our results show that O vacancy and non-metallic atoms X doped monolayer SnO are stable at room temperature by the formation energy and molecular dynamics simulations. Meanwhile, although doped atoms X and O vacancy lead to the local structure deformation in monolayer SnO, it does not break the fourfold coordination structure. Moreover, the non-metallic elements H, B, F, Si and P is induced magnetism in monolayer SnO system and the magnetic moments are 0.73, 1.11, 0.87, 2.15 and 0.81μB, respectively. The doping of non-magnetic elements enables p-type oxides to acquire magnetism, which further expands their applications in field of spintronics.

3‐Dimensional Scanning of Entire Unit Cells in Single Nanoparticles.

AbstractProperties of nanomaterials such as optical, electrical, and chemical properties are strongly correlated with lattice symmetry, making characterization of lattice symmetry essential. We introduce a symmetry analysis method using 3D atomic coordinates obtained by Brownian one‐particle 3D reconstruction. The method allows direct and quantitative analysis of symmetrical properties and delivers local structural characteristics of individual platinum (Pt) nanoparticles in unit‐cell level. Local structural deformations of the Pt nanoparticles such as lattice distortion and internal symmetry breakage are demonstrated, revealing that the crystal structure of sub‐3 nm Pt nanoparticles generally maintains FCC crystallinity and exhibits localized deviation from their bulk counterpart.

An aero-hydro coupled method for investigating ship collision against a floating offshore wind turbine

Ship collision hazards with floating offshore wind turbines (FOWTs) has been identified and the dynamic responses of FOWT under ship collision scenarios are necessary to be investigated. This paper develops a numerical solver to address the challenge of considering wind-wave loads in the ship-FOWT collision analysis. The user-defined load subroutine, LOADUD, in LS-DYNA is utilized to model the wind, wave and mooring loads. A simplified aerodynamic model considering blade pitch strategy is used and the hydrodynamic loads are calculated based on potential-flow theory with a linear wave kinematic model. The mooring forces are considered with a linearized model. The implementation of the coupled solver is verified by conducting free decay test, wave-only and wind-only analysis, respectively and comparing them with the reference values. Good agreement has been achieved, indicating that the aero-hydro coupling effects can be accurately simulated by the numerical solver. With the developed method and solver, cases of ship collision with a spar-type floating wind turbine are simulated and both local structural deformation and global motions in 6DOF are obtained. The influence of velocity, flexibility of tower, deformability of the ship, wind-wave loads are further discussed. It is found that the impact velocity can greatly affect the structural responses and a high-speed impact can directly lead to tower collapse. By comparing the cases of ship collision with FOWT, and those with fixed-support wind turbine, the flexibility of wind turbine tower is found to rarely influence the energy dissipation under collision scenario of FOWT, while it is important for the collision scenario of fixed-support wind turbine. The wind-wave condition can be more hazardous as a smaller impact velocity can lead to structures collapsing. This is because, even though the structure can withstand the ship collision, the residual strength may not be enough for the following wind loads, which can result in the structure to finally collapse. Additionally, the proposed fully coupled method is used to validate one of the authors’ previous studies, which is a decoupled method regarding the ship-FOWT collision analysis [1]. The external dynamic results from two methods are compared and discussed. Good agreement is reached between two methods for low-velocity impact but for high-speed collision or collisions with serious deformation, limitations of decoupled method can be found because some basic assumptions of them are violated. The proposed method and solver can be used to evaluate the crashworthiness of FOWT during the engineering design phase.

Solving 2-D Slamming Problems by an Improved Higher-Order Moving Particle Semi-Implicit Method

Abstract A higher-order moving particle semi-implicit (MPS) method was further developed to solve 2-D water entry problems. To overcome the inconsistency in the original MPS methods, a pressure gradient correction was implemented to guarantee the first-order consistency of the gradient. The corrective matrix was modified by using the derivative of the kernel function. A particle shifting technique was also applied to improve the numerical stability. Validation studies were carried out for water entry of a rigid wedge with the tilting angles of 0, 10, and 20, and two rigid ship sections. Convergence studies were conducted on domain size, particle spacing, and time step. A particle convergence index method was proposed to evaluate numerical uncertainties in the improved MPS method. Uncertainties in numerical solutions due to spatial discretization were calculated. The predicted impact pressures and forces by the present method are in good agreement with experimental data. Introduction Slamming can cause local structural deformation and damages. It is important to solve highly nonlinear water-entry problems involving breaking free surfaces. Many studies on the impact of pressures/ loads during water entry or slamming have been performed using experiments, analytical solutions, and numerical simulations. Extensive drop tests have been conducted. For example, Bisplinghoff and Doherty (1952) carried out a series of experiments for free-fall wedges. Because ship motions in waves can lead to asymmetric water entry, wedges with different tilt angles were tested by Barjasteh et al. (2016). A more detailed review of studies based on theoretical, potential-flow, and computational fluid dynamics (CFD) methods is presented in the work of Peng and Qiu (2018).

Graphene Origami-Enabled Auxetic Metallic Metamaterials: An Atomistic Insight

Auxetic metamaterials with programable negative Poisson's ratio (NPR) are of great significance in engineering applications. These materials, however, are either mechanically weak or heavily reliant on their specially designed architecture/topology to be auxetic. Consequently, their auxetic performance may be deteriorated or even lost due to local structural deformation or failure under excessive external loading. Developing materials simultaneously possessing auxetic characteristics and excellent mechanical properties still remains a great challenge. Herein, we report a class of graphene origami (GOri)-enabled metallic metamaterials with a highly tunable NPR as well as improved mechanical properties using molecular dynamics study. Simulation results reveal that embedding more GOri into Cu matrix can not only lead to a bigger NPR but also an increased elastic modulus of the nanocomposite. The NPR of the nanocomposite with 3.35 wt % Miura-patterned GOri can reach –0.2796 at room temperature. The application of pressure and temperature can further enhance the auxetic behavior of the nanocomposite. It is also found that GOri/Cu nanocomposite significantly outperforms its counterpart reinforced with pristine graphene in terms of NPR.

Electrochemical Potential of the Metal Organic Framework MIL-101(Fe) as Cathode Material in Li-Ion Batteries

We discuss the characteristic factors that determine the electrochemical potentials in a metal-organic framework used as cathode for Li-ion batteries via density functional theory-based simulations. Our focus is on MIL-101(Fe) cathode material. Our study gives insight into the role of local atomic environment and structural deformations in generating electrochemical potential.

Elucidation of local structure deformation in κ−(BEDT−TTF)2Cu[N(CN)2]Br by x-ray fluorescence holography

$\ensuremath{\kappa}\text{\ensuremath{-}}{(\mathrm{BEDT}\text{\ensuremath{-}}\mathrm{TTF})}_{2}\mathrm{Cu}[\mathrm{N}{(\mathrm{CN})}_{2}]\mathrm{Br} (\ensuremath{\kappa}\text{\ensuremath{-}}\mathrm{Br})$ is an organic superconductor that changes to an Anderson-type insulator due to the random defects introduced by x-ray irradiation. In this study, we directly investigated the effects of irradiation on the local structures in the anion layer of $\ensuremath{\kappa}\text{\ensuremath{-}}\mathrm{Br}$ using x-ray fluorescence holography. The local structures around the Cu atoms in the anion layer were directly reconstructed from holograms. Prior to radiation damage, the reconstruction clearly shows the atomic images of the Br and N atoms that are directly coordinated to Cu. In the irradiated samples, the N images in the reconstructions were strongly suppressed as a result of the positional fluctuations of N introduced by the defects induced by irradiation. Using the previously proposed ``bond-shifted'' model and the thermal vibration amplitudes calculated from molecular dynamics simulations, we simulated the holograms and the atomic reconstructions of the anion layer. The simulations show that the ``bond-shifted'' model, along with thermal vibrations at 100 K, suppresses the N atomic images, as was observed in the experimental reconstructions.

Interferometric 4D-STEM for Lattice Distortion and Interlayer Spacing Measurements of Bilayer and Trilayer 2D Materials.

Van der Waals materials composed of stacks of individual atomic layershave attracted considerable attention due to their exotic electronic properties that can be altered by, e.g., manipulating the twist angle of bilayer materials or the stacking sequence of trilayer materials. To fully understand and control the unique properties of these few-layer materials, a technique that can provide information about their local in-plane structural deformations, twist direction, and out-of-plane structure is needed. In principle, interference in overlap regions of Bragg disks originating from separate layers of a material encodes 3D information about the relative positions of atoms in the corresponding layers. Here, an interferometric 4D scanning transmission electron microscopy technique is described that utilizes this phenomenon to extract precise structural information from few-layer materials with nm-scale resolution. It is demonstrated how this technique enables measurement of local pm-scale in-plane lattice distortions as well as twist direction and average interlayer spacings in bilayer and trilayer graphene, and therefore provides a means to better understand the interplay between electronic properties and precise structural arrangements of few-layer 2D materials.

Seismic response of large-span spatial structures under multi-support and multidimensional excitations including rotational components

To achieve rational and precise seismic response predictions of large span spatial structures (LSSSs), the inherent non-uniformity and multidimensionality characteristics of earthquake ground motions should be properly taken into consideration. However, due to the limitations of available earthquake stations to record seismic rotational components, the effects of rocking and torsional earthquake components are commonly neglected in the seismic analyses of LSSSs. In this study, a newly developed method to extract the rocking and torsion components at any point along the area of a deployed dense array from the translational earthquake recordings is applied to obtain the rotational seismic inputs for a LSSS. The numerical model of an actual LSSS, the Dalian International Conference Center (DICC), is developed to study the influences of multi-support and multidimensional excitations on the seismic responses of LSSSs. The numerical results reveal that the non-uniformity and multidimensionality of ground motion input can considerably affect the dynamic response of the DICC. The specific degree of influence on the overall and local structural displacements, deformations and forces are comprehensively investigated and discussed.

Probing the deformation of [12]cycloparaphenylene molecular nanohoops adsorbed on metal surfaces by tip-enhanced Raman spectroscopy.

[n]Cycloparaphenylene ([n]CPP) molecules have attracted broad interests due to their unique properties resulting from the distorted and strained aromatic hoop structures. In this work, we apply sub-nanometer resolved tip-enhanced Raman spectroscopy (TERS) to investigate the adsorption configurations and structural deformations of [12]CPP molecules on metal substrates with different crystallographic orientations. The TERS spectra for a [12]CPP molecule adsorbed on the isotropic Cu(100) surface are found to be essentially the same over the whole nanohoop, indicating an alternately twisted structure that is similar to the [12]CPP molecule in free space. However, when the [12]CPP molecules are adsorbed on the anisotropic Ag(110) surface, the molecular shape is found to be severely deformed into two types of adsorption configurations: one showing an interesting "Möbius-like" feature and the other showing a symmetric bending structure. Their TERS spectral features are found to be site-dependent over the hoop and even show peak splitting for the out-of-plane C-H bending vibrations. The deformed structural models gain strong support from the spatial distribution of "symmetric" TERS spectra at different positions on the hoop. Further TERS imaging, with a spatial resolution down to ∼2 Å, provides a panoramic view on the local structural deformations caused by different tilting of the benzene units in real space, which offers insights into the subtle changes in the aromatic properties over the deformed hoop owing to inhomogeneous molecule-substrate interactions. The ability of TERS to probe the molecular structure and local deformation at the sub-molecular level, as demonstrated here, is important for understanding surface science as well as molecular electronics and optoelectronics at the nanoscale.

Slamming load and hydroelastic structural response of bow flare areas of aluminium fast displacement crafts

The paper evaluates the response of an aluminium stiffened panel of a fast displacement craft under bow flare slamming loads by using three finite element methods: (1) a linear static analysis to calculate the structural elastic deformation and stress under the design load; (2) an independent analysis of the slamming load and the elastic structural response (a decoupled method); (3) a method that couples their interaction (a fully coupled method). These methods are compared to analyse the hydroelastic effect when predicting the structural loading and response. Similar results are obtained by the three methods and the linear static analysis based on design load evaluates with accuracy the local structural deformation and stress. The primary objective of the present work is to investigate the strength and safety of bow-flared structures when designing high-speed and fast displacement aluminium crafts subjected to slamming pressure loads. The influence of spray rail on the bow-flared slamming pressures and the effect of boundary conditions on the elastic structural responses are discussed.

Mechanistic insight into gold nanorod transformation in nanoscale confinement of ZIF-8

Core-shell hybrid nanomaterials have shown new properties and functions that are not attainable by their single counterparts. Nanoscale confinement effect by porous inorganic shells in the hybrid nanostructures plays an important role for chemical transformation of the core nanoparticles. However, metal-organic frameworks (MOFs) have been rarely applied for understanding mechanical insight into such nanoscale phenomena in confinement, although MOFs would provide a variety of properties for the confining environment than other inorganic shells such as silica and zeolite. Here, we examine chemical transformation of a gold nanorod core enclosed by a zeolitic imidazolate framework (ZIF) through chemical etching and regrowth, followed by quantitative analysis in the core dimension and curvature. We find the nanorod core shows template-effective behavior in its morphological transformation. In the etching event, the nanorod core is spherically carved from its tips. The regrowth on the spherically etched core inside the ZIF gives rise to formation of a raspberry-like branched nanostructure in contrast to the growth of an octahedral shape in bulk condition. We attribute the shell-directed regrowth to void space generated at the interfaces between the etched core and the ZIF shell, intercrystalline gaps in multi-domain ZIF shells, and local structural deformation from the acidic reaction conditions.