Local Structure Research Articles

Synergistic contributions of the poling field-induced changes in local structure on the piezoelectric properties of modified BaTiO3 system

Abstract Local structural heterogeneity is a key factor in improving the piezoelectric properties of non-centrosymmetric piezoelectric systems. This work investigates electric field-induced structural and microstructural changes at localized and average scales to elucidate the structure-property correlations that enhance piezoelectric performance in Sn-doped BaTiO3 systems exhibiting coexisting phase boundaries. Despite showing field-induced structural phase transformation, the sample displays variations in piezocoefficient values with the nature of phase boundary compositions. Raman spectroscopy measurements reveal that the TiO6/SnO6 octahedra near the tetragonal-orthorhombic phase boundary exhibit significantly greater poling field-induced structural heterogeneities in local structure compared to those near the orthorhombic-cubic phase boundary. X-ray absorption spectroscopic results on Ti and Sn K-edge in unpoled and poled samples reveal that the dipolar contribution responsible for the piezoelectricity originates from field-induced distortion associated with both TiO6 and SnO6 octahedra. Near the vicinity of the tetragonal-orthorhombic phase boundary, both the TiO6 and SnO6 contributions are cumulative and exhibit better piezoelectricity. On the other hand, at the orthorhombic-cubic phase boundary, the dipolar contributions from these octahedra are counterintuitive, resulting in a reduction of piezoelectricity. These results could provide a pathway to design materials with an enhanced piezoelectric response by considering various phase boundary aspects before applying a poling field prior to making them piezoactive.

Intersectionality shapes the access to various adaptive resources in climate-vulnerable contexts

Abstract Intersectional approaches are becoming essential to understanding the differential impacts of climate change and the heterogeneity of adaptive capacities. Varying factors of social and economic privileges and inequalities synergistically shape the local power structure, ultimately determining disproportionality and unequal access to adaptive resources. Using empirical data from coastal Bangladesh, which is part of the Ganges Delta, and one of the world’s -most climate-vulnerable regions, this study shows how religion, gender, and ethnicity intersect with patterns in (i) farm and non-farm incomes, (ii) land conflicts, (iii) the size of farms, and (iv) access to critical sources of weather information. The study highlights that multilayered identity, which is shaped by various structural determinants, including local power structure, can determine gendered dimensions of access to various adaptation resources. It also shows that if policymakers and development partners partially understand or do not understand the complex landscape of local vulnerability or unequal power structures including the adaptive capacity of the vulnerable populations, they would not be able to provide critical support in times of crisis. The concept of intersectionality is therefore critical in addressing adaptation and risk management challenges for regions like the Ganges Delta and other parts of the world, where people are struggling with similar social and environmental challenges.

A Broad-High Temperature Ceramic Capacitor with Local Polymorphic Heterogeneous Structures.

Crafting high-performance dielectrics tailored for pulsed power capacitors, in response to the escalating demands of practical applications, presents a formidable challenge. Herein, this work introduces a novel lineup of lead-free ceramics with local polymorphic heterogeneous structures, defined by the formula (1-x)[0.92BaTiO3-0.08Sr(Mg1/2Ti3/4)O3]-x(Na0.5Bi0.5)TiO3 (BT-SMT-xNBT). This innovative multi-scale synergistic strategy, spanning from the atomic to grain scale, yields materials with a giant recoverable energy density (Wrec) of 10.1 J·cm-3 and an impressive energy efficiency (η) of 95.0%. The integration of linear end elements SMT can significantly mitigate the polarization hysteresis while concurrently boosting the breakdown strength, thus enhancing overall energy efficiency. Furthermore, the inclusion of NBT with high polarization serves to amplify domain size, thereby reinforcing the electric field-induced polarization. This addition also stimulates the creation of polymorphic heterostructures, where tetragonal and rhombohedral nanodomains coexist, as validated by aberration-corrected transmission electron microscopy. Notably, the BT-SMT-0.2NBT ceramics have demonstrated outstanding high-temperature energy storage capabilities, with a Wrec of 7.2 J·cm-3 and an η of 92.2% at 150 °C, along with remarkable broad-temperature stability (ΔWrec, Δη ≤ 4.0%, ≈20-150 °C). These achievements in this work propel the field toward more practical and durable solutions of energy storage dielectrics.

Five-analyzer Johann spectrometer for hard X-ray photon-in/photon-out spectroscopy at the Inner Shell Spectroscopy beamline at NSLS-II: design, alignment and data acquisition.

Here, a recently commissioned five-analyzer Johann spectrometer at the Inner Shell Spectroscopy beamline (8-ID) at the National Synchrotron Light Source II (NSLS-II) is presented. Designed for hard X-ray photon-in/photon-out spectroscopy, the spectrometer achieves a resolution in the 0.5-2 eV range, depending on the element and/or emission line, providing detailed insights into the local electronic and geometric structure of materials. It serves a diverse user community, including fields such as physical, chemical, biological, environmental and materials sciences. This article details the mechanical design, alignment procedures and data-acquisition scheme of the spectrometer, with a particular focus on the continuous asynchronous data-acquisition approach that significantly enhances experimental efficiency.

Legacy and Novel Per- and Polyfluoroalkyl Substances in Surface Soils across China: Source Tracking and Main Drivers for the Spatial Variation.

China aims to actively control the contamination of globally concerning per- and polyfluoroalkyl substances (PFASs). Evaluation of the current situation can provide a critical reference point for tracking the effectiveness of ongoing progress. Herein, we present the first comprehensive assessment of the spatial variations of 20 legacy and 54 novel PFASs in Chinese background soils in 2021. Novel PFASs were extensively detected in 98.4% of the samples, with 21 species being first reported, which greatly facilitated the appointment of diverse emission sources that aligned with local industrial structures. However, legacy PFASs still dominated the ∑74PFAS profile (median 0.51 ng/g, 0.050-8.33 ng/g). The spatial heterogeneity of soil PFASs was positively driven by economic development and atmospheric deposition, enabling the establishment of predictive models to project the national distribution and temporal trends. Elevated PFAS levels were predominantly distributed in the more industrialized eastern and southern regions, as well as other coastal areas with greater precipitation. ∑74PFAS in surface soils was estimated to increase by 12.9 pg/(g year) over 2002-2021, which would continue alongside economic growth, albeit with greater contributions from novel alternatives. Our work provides comprehensive baseline and predictive data to inform policies toward PFAS control in China.

Alleviating the resolution limit problem in spatial community detection: a local network structure-based method

Spatial community detection plays a crucial role in the analysis of spatially embedded networks. However, most existing methods adopt modularity as an objective function, which may fail to detect small spatial communities (i.e. the well-known resolution-limit problem). To alleviate this problem, a local network structure-based spatially constrained Leiden method was developed. First, the weights of the edges were reset based on the local network structure, which facilitated a clearer delineation between distinct communities. Second, we extended Leiden, an effective community detection method, to spatial community detection content by adding spatial constraints. Experiments on simulated datasets demonstrated that the proposed method is superior to four state-of-the-art methods for detecting spatial communities of different sizes. A case study conducted using the Shenzhen taxi dataset demonstrated that the proposed method outperformed four state-of-the-art methods in revealing urban spatial structures. Notably, the modularity of the spatial communities detected using the proposed method exhibited a marked improvement, nearly doubling that of the four comparative methods in the case study. This study presents a novel and promising framework for detecting spatial communities using modularity.

Probing Nanoscale Charge Transport Mechanisms in Quasi-2D Halide Perovskites for Photovoltaic Applications.

Quasi-2D layered halide perovskites (quasi-2DLPs) have emerged as promising materials for photovoltaic (PV) applications owing to their advantageous bandgap for absorbing visible light and the improved stability they enable. Their charge transport mechanism is heavily influenced by the grain orientation of their crystals as well as their nanostructures, such as grain boundaries (GBs) and edge states─the formation of which is inevitable in polycrystalline quasi-2DLP thin films. Despite their importance, the impact of these features on charge transport remains unexplored. In this study, we conduct a detailed investigation on polycrystalline quasi-2DLP thin films and devices, carefully analyzing how grain orientation and nanostructures influence charge transport. Employing nondestructive atomic force microscopy (AFM) topography, along with transient absorption spectroscopy (TAS) and grazing-incidence wide-angle X-ray scattering (GIWAXS), we obtained significant insights regarding the phase purity, crystallographic information, and morphologies of these films. Moreover, our systematic investigation using AFM-based techniques, including Kelvin probe force microscopy (KPFM) and conductive AFM (c-AFM), elucidates the roles played by GBs and edge states in shaping charge transport behavior. In particular, the local band structure along the GBs and edge states within both vertical and parallel grains was found to selectively repel electrons and holes, thus facilitating charge carrier separation. These findings provide perspectives for the development of high-performance quasi-2DLP PV devices and highlight potential approaches that can leverage the intrinsic properties of quasi-2DLPs to advance the performance of perovskite solar cells.

War Reparations, Structural Change, and Intergenerational Mobility

Abstract From 1944 to 1952, largely agrarian Finland had to export, on average, 4% of its yearly GDP in industrial products to the Soviet Union as war reparations. To meet the reparation demands, the Finnish state needed to provide extensive but temporary support to Soviet-assigned industries with insufficient production capacity. This paper documents the long-term impacts of this extensive and temporary industrial policy on industrial and local development and on individual outcomes. Using newly digitized datasets, I show in a difference-in-differences setup that the short-term nonmarket production persistently and significantly increased the employment and production of the manufacturing industries exposed to the policy. These industries plausibly benefited from large initial investments and exposure to export markets associated with the war reparations. The episode further led to local development and structural change, as the more exposed regions became persistently more industrialized. I substantiate these within-Finland results with triple-difference setups employing comparable Norwegian data. I further use Finnish administrative data to study the long-term individual impacts of the episode. Tracking individuals over 30 years, I show that the initial state investments and the persistent change in the local industrial structure increased long-term incomes, led to more educational attainment, and promoted the upward mobility of children and young adults living in the more exposed regions prior to the war reparations period. The observed effects are driven by the more advanced heavy industry, which received the majority of state assistance.

Organic‐Inorganic Hybrid Material for Photocatalytic H₂ Evolution: Electron Shuttling between Photoresponsive Nanocomposite and Co(II) Redox Mediator

AbstractIn this report, a conductive polymer encapsulated metal oxide photocatalyst is developed through a straightforward insitu synthesis method wherein, polythiophene is incorporated with TiO2 nanoparticles which imparts enhanced visible‐light absorption to the samples and significantly improves the efficiency of charge transfer resulting due to the vacancy defects and high conductivity, ultimately leading to exceptional performance in H2 production. Significantly, the rate of H2 production was enhanced even further through the deposition of simple redox mediator. The introduction of Co2+ facilitates the transfer of photogenerated holes from the valence band by its conversion from +2 to +3 oxidation state which further enables the oxidation mechanism. The recombination rate of excitons has been significantly reduced due to the efficient transfer of photogenerated holes and the rate of photocatalytic H2 production is improved. Interestingly, the valence states and local atomic structure of the Ti species in the synthesized sample were ascertained through the utilization of Ti K‐edge XANES and EXAFS analysis, which validated the energy position.

AGCNAF: predicting disease-gene associations using GCN and multi-head attention to fuse the similarity features

Abstract Association prediction between diseases and genes is a critical step in revealing the molecular mechanisms of diseases and developing drug treatment strategies. With the explosive growth of data in the biomedical field, how to effectively utilize these data for accurate prediction has become a hotspot and challenge in current research. To overcome the limitations of current prediction methods in dealing with complex biological network structures and feature extraction, this study proposes AGCNAF, a method that combines an unsupervised Graph Convolutional Network (GCN) and a multi-head attention mechanism. The metagraph-guided random walk strategy enables AGCNAF to capture local and high-order topological structures in the graph, while GCN is responsible for realizing deep feature extraction of these structures. By incorporating similarity features through the multi-attention mechanism, AGCNAF achieves effective integration of global and local features, which significantly improves the prediction performance. By incorporating similarity features through the multi-attention mechanism, AGCNAF achieves effective integration of global and local features, which significantly improves the prediction performance. By utilizing the machine learning binary classification model for prediction, the experimental results through five-fold cross-validation show that AGCNAF demonstrates significant advantages in prediction performance compared to existing methods, with its AUC and AUPR reaching 0.9686 and 0.9709, respectively, and the AUC up to 0.9812 under specific conditions. 
To verify the practical application value of AGCNAF, this study also conduct case studies on Alzheimer's disease, lung cancer, and breast cancer. The results further confirm the excellent performance of AGCNAF in identifying potential disease-gene associations, which opens up new possibilities for future disease-gene research.

Lessons from a participatory community cricket breeding project in Vientiane Province, Lao PDR

Abstract Edible insect production is a key tool for sustainable development and global food security, but its social dimensions and the organisation of farming operations remain understudied. Crickets are among the most recognised edible insects for farming and offer appealing development opportunities for Lao PDR – a Southeast Asian country whose cricket farming sector has lagged behind neighbouring Thailand and which continues to experience challenging economic and food security conditions. Concerning these sustainable development and research priorities, this paper presents the case study analysis of a service evaluation of Cricket Lao Farm, which implemented a project on the distributed (off-site) production of crickets among local community members. Data collection took place from September to November 2023 and included a survey with 30 participants complemented by qualitative information from discussion groups, home visits, informal conversations, and project documentation. While small-scale farming operations ended within a year due to widespread cricket mortality of unknown cause, community-based cricket farming was in principle profitable and demonstrated strong development potential and local relevance. Furthermore, most of the community-based farmers were motivated and interested in resuming operations in the future. The analysis of this case offers important lessons for further development of the cricket farming sector in Lao PDR, highlighting the challenges of the Western social enterprise model in a development setting, the need to actively manage participation, and to develop an understanding of local community structures before commencing operations. To ensure future success, projects should include robust monitoring and evaluation plans; regular and bidirectional communication between community members and the central farm; co-development of breeding strategies, response plans, and good animal husbandry practices; and community engagement activities involving local schools.

Non-monotonic dynamic correlation explored via active microrheology

Abstract In the study of local and heterogeneous structures in supercooled liquids, microrheology plays a crucial role, offering a closer examination of the mechanical properties at a local level. We concentrate on active microrheology, where an external force drives a probe particle. This technique is employed in the study of a Kob–Andersen mixture, using extensive molecular dynamics simulations. Through active microrheology, we analyze the positional dependence of viscosity, observing how probe particles respond to activation velocity. Utilizing advanced stochastic analysis, we disentangle the deterministic and stochastic components of the local viscosity time series, characterizing its nonlinear and intermittent properties, which indicate heterogeneity. We construct a Langevin equation to model the dynamics of local viscosity and derive its drift and diffusion coefficients from simulation data. Additionally, we investigate the temperature-dependent variations of viscosity dynamics, unveiling their multiplicative and nonlinear nature. We elaborate on how the existence of multiplicative dynamics in viscosity results in the characteristic emergence of heterogeneity within viscosity dynamics. We derive a dynamic correlation length from local viscosity. Moreover, this correlation length shows a non-monotonic dependence on temperature with a maximum at about the Kauzmann temperature.

Mapping domain structures near a grain boundary in a lead zirconate titanate ferroelectric film using X-ray nanodiffraction

The effect of an electric field on local domain structure near a 24° tilt grain boundary in a 200 nm-thick Pb(Zr0.2Ti0.8)O3 bi-crystal ferroelectric film was probed using synchrotron nanodiffraction. The bi-crystal film was grown epitaxially on SrRuO3-coated (001) SrTiO3 24° tilt bi-crystal substrates. From the nanodiffraction data, real-space maps of the ferroelectric domain structure around the grain boundary prior to and during application of a 200 kV cm−1 electric field were reconstructed. In the vicinity of the tilt grain boundary, the distributions of densities of c-type tetragonal domains with the c axis aligned with the film normal were calculated on the basis of diffracted intensity ratios of c- and a-type domains and reference powder diffraction data. Diffracted intensity was averaged along the grain boundary, and it was shown that the density of c-type tetragonal domains dropped to ∼50% of that of the bulk of the film over a range ±150 nm from the grain boundary. This work complements previous results acquired by band excitation piezoresponse force microscopy, suggesting that reduced nonlinear piezoelectric response around grain boundaries may be related to the change in domain structure, as well as to the possibility of increased pinning of domain wall motion. The implications of the results and analysis in terms of understanding the role of grain boundaries in affecting the nonlinear piezoelectric and dielectric responses of ferroelectric materials are discussed.

Multi-scale and time-resolved structure analysis of relaxor ferroelectric crystals under an electric field

Lead-based relaxor ferroelectrics exhibit giant piezoelectric properties owing to their heterogeneous structures. The average and local structures measured by single-crystal X-ray diffraction under DC and AC electric fields are reviewed in this article. The position-dependent local lattice strain and the distribution of polar nanodomains and nanoregions show strong electric field dependence, which contributes to the giant piezoelectric properties.

Mechanisms of separation of the elastic step and the thermal step

The elastic interaction causes a two‐step conversion from the low‐spin (LS) to the high‐spin state (HS) following a femtosecond laser pulse excitation. These steps occur on different timescales: a spin conversion (elastic step) in a short time due to pressure propagation and a late spin conversion (thermal step) resulting from heat diffusion. In this paper, we provide a brief review of models for spin crossover phenomena, emphasizing the role of the difference of degeneracy of the HS state and LS state and elastic interaction due to changes in local structures. We also review theoretical approaches to these effects. Additionally, to analyze the dynamical process of spin conversion after photo‐irradiation, it is necessary to consider mechanisms of heat transfer among spins. Recently, we proposed a two‐temperature model that incorporates both lattice and spin temperatures, which enables us to reproduce the two steps under an early uniformization of the lattice temperature, highlighting the importance of the timescales of these processes. Furthermore, we explore possible mechanisms to separate the two steps by examining the different timescales of processes of spin conversions by mechanical and entropic forces, and also by considering changes of local temperature due to spin conversion.

Ab Initio Simulation of Raman Fingerprints of Sulfur/Carbon Copolymer Cathodes During Discharge of Li-S Batteries.

Sulfur/carbon copolymers have emerged as promising alternatives for conventional crystalline sulfur cathodes for lithium-sulfur batteries. Among these, sulfur--n--1,3--diisopropenylbenzene (S/DIB) copolymers, which present a 3D network of DIB molecules interconnected via sulfur chains, have particularly shown a good performance and, therefore, have been under intensive experimental and theoretical investigations. However, their structural complexity and flexibility have hindered a clear understanding of their structural evolution during redox reactions at an atomistic level. Here, by performing state-of-the-art ab initiomolecular dynamics-based Raman spectroscopy simulations, we investigate the spectral fingerprints of S/DIB copolymers arising from local structures during consecutive reactions with lithium. We discuss Raman spectral changes in particular frequency ranges which are common in S/DIB copolymers having shortand those consisting of longer sulfur chains. We also highlight those spectroscopic fingerprints specific to local S/DIB structures containing only short or long sulfur chains. This could help distinguish them experimentally during discharge. Our theoretically predicted results are in a good agreement with experimental Raman measurements on cells at different discharge stages. This work representsan attempt to compute Raman fingerprints ofcopolymer cathodes during battery operationincluding quantum-chemical and finite-temperature effects, and provides a guideline for Raman spectral changes of arbitrary electrodes during discharge.

Origin of unique electronic structures of single-atom alloys unraveled by interpretable deep learning.

We uncover the origin of unique electronic structures of single-atom alloys (SAAs) by interpretable deep learning. The approach integrates tight-binding moment theory with graph neural networks to accurately describe the local electronic structure of transition and noble metal sites upon perturbation. We emphasize the complex interplay of interatomic orbital coupling and on-site orbital resonance, which shapes the d-band characteristics of an active site, shedding light on the origin of free-atom-like d-states that are often observed in SAAs involving d10 metal hosts. This theory-infused neural network approach significantly enhances our understanding of the electronic properties of single-site catalytic materials beyond traditional theories.

A conceptual and numerical model of fluid flow and heat transport in the Topusko hydrothermal system

Comprehensive understanding of hydrothermal systems is often obtained through the integration of conceptual and numerical modelling. This integrated approach provides a structured framework for the reconstruction and quantification of fluid dynamics in the reservoir, thereby facilitating informed decision-making for sustainable utilisation and environmental protection of the hydrothermal system. In this study, an updated conceptual model of the Topusko hydrothermal system (THS; central Croatia) is proposed based on structural, geochemical, and hydrogeological analyses. The stratigraphic sequence and the structural framework of the THS were defined based on geological maps and field investigations. As depicted by hydrochemical and isotope analyses, thermal waters in Topusko (temperatures of up to 65 °C) are of meteoric origin and circulate in a carbonate aquifer. The THS receives diffuse recharge approximately 13 km S from Topusko, where Triassic carbonates crop out. Gravity-driven regional groundwater circulation is favoured by regional thrusts that tectonically uplifted Palaeozoic low permeable rocks. These structures confine the fluid flow in the permeable, fractured and karstified, Triassic carbonates favouring the northward circulation of the water. A regional anticline lifts the aquifer closer to the surface in Topusko. Open fractures in the anticline hinge zone increase the fracturing and permeability field of the aquifer promoting the quick upwelling of the thermal water resulting in the Topusko thermal springs. Numerical simulations of fluid flow and heat transport corroborate the proposed conceptual model. In particular, a thermal anomaly was modelled in the Topusko subsurface with temperature values of 31.3 °C and 59.5 °C at the surface and at the base of the thermal aquifer, respectively, approaching the field observations. These findings showed that the circulation of Topusko thermal water is influenced by regional and local geological structures suggesting that the enhanced permeability field in the discharge area enables the formation of the natural thermal springs.

Singularities of worldsheets along framed particle trajectories in Minkowski three-space

Modeling the worldsheets along the trajectory (a string) of a point particle (a 0-brane) as two timelike surfaces in 3-subspace of Minkowskian spacetime, respectively, the work aims at analyzing the topological structures of these two worldsheets along the trajectory of the point particle from the view point of singularity theory. Different from the regular curves, the traveling trajectory (modeled as framed timelike curve) of the particle is allowed to be singular, two worldsheets are generated by the traveling trajectories of the particle. As applications of singularity theory, we classify the singularities of these two worldsheets along the traveling trajectory of the particle. Using the approach of the unfolding theory in singularity theory, we find two new geometric invariants which are useful for characterizing the local topological structures of singularities of these two worldsheets along the particle. It is revealed that there exist cuspidal edge type and swallowtail type of singularities for these two worldsheets under the appropriate conditions of geometric invariants. Meanwhile, it is also pointed out that the types of singularities of these two worldsheets have a close relationships to the order of contacts between these two worldsheets and two timelike planes, respectively. Finally, some examples are presented to interpret our theoretical results.

Boosting Photoluminescence of Rare-Earth-Based Double Perovskites by Isoelectronic Doping of ns2 Metal Ions.

Doping of ns2 metal ions as an energy transfer (ET) bridge can significantly elevate the photoluminescence properties. Nonetheless, the fundamental influence of ns2 metal ions on the local lattice structures remains unclear, hindering the advancement of functional materials. Herein, Sb3+ doped rare earth double perovskites is employed as a typical case to demonstrate this issue. It is found that the isoelectronic doping of Sb3+ ions not only enhances the ET efficiency but also changes their localized electronic and lattice structures. Both density functional theory (DFT) and Judd-Ofelt (J-O) theory calculations provide unambiguous evidence that the isoelectronic doping of Sb3+ ions enables a more localized charge density in the [LnCl6]3- (Ln: Lanthanide) octahedron and reduces the symmetry of the environment around the Ln3+, facilitating the radiative transition rates of Ln3+ while enhancing their ET efficiency. Compared with Cs2NaScCl6:Ln3+, the ET efficiency of Cs2NaScCl6:Sb3+/Ln3+ is enhanced by 1.5-fold, reaching up to 98.3%. To the best of available knowledge, this work is the first to unravel the intrinsic mechanism of enhanced ET process enabled by isoelectronic doping via DFT and J-O theory. This research sheds light on understanding the mechanism of photophysics and rational design of the functional perovskite materials.