Preferential segregation of gold at the symmetrical tilt grain boundaries of platinum: an atomic-scale quantitative understanding.

Grain boundary (GB) segregation plays a pivotal role in maintaining and optimizing the remarkable catalytic or mechanical properties of nanocrystalline Pt by reducing the Gibbs free energy and thereby impeding structure degradation. The solute segregation behavior at the Pt GB, however, is not well understood at the atomic level. In this study, we employed first-principles calculations to elucidate the preferential segregation behavior of a single Au atom at the symmetrical tilt GB of Pt. For pure Pt, a linear relationship between the GB energy and excess volume is observed. Therefore, Au exhibits strong segregation tendencies towards GB to release excess energy and volume stored at the strained GB. Although the segregation energy is sensitive to various GB sites, it is interesting to note that the minimum one increases linearly with GB energy. This site-sensitivity of segregation energy can be attributed to mechanical, chemical, and interaction parts, which are quantitatively related to the atomic volume, coordination number, and average bond length, respectively. Finally, the interplay among different structural descriptors is revealed. These insights into the association between GB structures, segregation configuration and energy offers valuable atomic-scale quantitative insights into the segregation behavior of Au in Pt GBs, which holds significant implications for the design of Pt nanomaterials with enhanced thermal stability via GB engineering.

Site-specific reactivity of stepped Pt surfaces driven by stress release.

Heterogeneous catalysts are widely used to promote chemical reactions. Although it is known that chemical reactions usually happen on catalyst surfaces, only specific surface sites have high catalytic activity. Thus, identifying active sites and maximizing their presence lies at the heart of catalysis research1-4, in which the classic model is to categorize active sites in terms of distinct surface motifs, such as terraces and steps1,5-10. However, such a simple categorization often leads to orders of magnitude errors in catalyst activity predictions and qualitative uncertainties of active sites7,8,11,12, thus limiting opportunities for catalyst design. Here, using stepped Pt(111) surfaces and the electrochemical oxygen reduction reaction (ORR) as examples, we demonstrate that the root cause of larger errors and uncertainties is a simplified categorization that overlooks atomic site-specific reactivity driven by surface stress release. Specifically, surface stress release at steps introduces inhomogeneous strain fields, with up to 5.5% compression, leading to distinct electronic structures and reactivity for terrace atoms with identical local coordination, and resulting in atomic site-specific enhancement of ORR activity. For the terrace atoms flanking both sides of the step edge, the enhancement is up to 50 times higher than that of the atoms in the middle of the terrace, which permits control of ORR reactivity by either varying terrace widths or controlling external stress. Thus, the discovery of the above synergy provides a new perspective for both fundamental understanding of catalytically active atomic sites and design principles of heterogeneous catalysts.

Magnesium Mitigation Behavior in P2-Layered Sodium-Ion Battery Cathode.

Heteroatom incorporation can effectively suppress the phase transition of layered sodium-ion battery cathode, but heteroatom behaviors during operating conditions are not completely understood at the atomic scale. Here, density functional theory calculations are combined with experiments to explore the mitigation behavior of Mg dopant and its mechanisms under operating conditions in P2-Na0.67Ni0.33Mn0.67O2. The void formed by Na extraction will pump some Mg dopants into Na layers from TM layers, and the collective diffusion of more than one Mg ion most likely occurs when the Mg content is relatively high in the TM layer, finally aggregating to form Mg-enrich regions (i.e., Mg segregation) apart from Ni vacancies. The void-pump-effect-induced Mg segregation effectively suppresses the P2-O2 phase transition owing to the stronger Mg-O electrostatic attraction that enhances the integrate of two adjacent oxygen layers and prevents the crack growth by mitigating the lattice volume variation under high-voltage cycling. Our work provides a fundamental understanding of heteroatom mitigation behavior in layered cathodes at the atomic level for next-generation energy storage technologies.

The effect of antisite defects on the mechanical and dynamic stability of Nb3Al.

The A15-type conventional superconductor Nb3Al alloys has been considered as an ideal candidate for next generation high field magnets due to its higher superconducting properties and less sensitivity to stain than that of industrialized Nb3Sn superconductor. First-principles methods are employed to study the potential point defects, vacancy and antisite defects in deviating stoichiometric Nb3Al alloys and their effect on structure and mechanical properties. Our results show that antisite defects are easier to be produced than vacancy defects, and NbAlantisite defects can keep the tetragonal structure of Nb3Al. Furthermore, the influence of antisite defects on dynamic stability of Nb3Al is investigated together with NbAldefects. With the increase of Nb antisite defect content and the formation of orderly arrangement, we found the phonon spectrum yields no more soft phonon modes, which is in contradiction with the dynamical instability of stoichiometric Nb3Al with no defects. Our calculations indicate Nb antisite defects play a crucial role on the dynamic stability of Nb3Al compounds.

In Situ Visualization of the Pinning Effect of Planar Defects on Li Ion Insertion.

Longevity of Li ion batteries strongly depends on the interaction of transporting Li ions in electrode crystals with defects. However, detailed interactions between the Li ion flux and structural defects in the host crystal remain obscure due to the transient nature of such interactions. Here, by in situ transmission electron microscopy and density function theory calculations, we reveal how the diffusion pathways and transport kinetics of a Li ion can be affected by planar defects in a tungsten trioxide lattice. We uncover that changes in charge distribution and lattice spacing along the planar defects disrupt the continuity of ion conduction channels and dramatically increase the energy barrier of Li diffusion, thus, arresting Li ions at the defect sites and twisting the lithiation front. The atomic-scale understanding holds critical implications for rational interface design in solid-state batteries and solid oxide fuel cells.

Bilayer tetragonal AlN nanosheets as potential cathodes for Li-O2 batteries.

Li-O2 batteries are considered promising electrochemical energy storage devices due to their high specific capacity and low cost. However, this technology currently suffers from two serious problems: low round-trip efficiency and slow reaction dynamics at the cathode. Solving these problems requires designing novel catalysis materials. In this study, a bilayer tetragonal AlN nanosheet as the catalyst is theoretically designed for the Li-O2 electrochemical system, and the discharge/charge process is simulated by a first-principles approach. It is found that the reaction path leading to Li4O2 is energetically more favored than the path to form a Li4O4 cluster on an AlN nanosheet. The theoretical open-circuit voltage for Li4O2 is 2.70 V, which is only 0.14 V lower than the formation of Li4O4. Notably, the discharge overpotential for forming Li4O2 on the AlN nanosheet is only 0.57 V, and the corresponding charge overpotential is as low as 0.21 V. A low charge/discharge overpotential can effectively solve the problems of low round-trip efficiency and slow reaction kinetics. The decomposition pathways of the final discharge product Li4O2 and the intermediate product Li2O2 are also investigated, and the decomposition barriers are 1.41 eV and 1.45 eV, respectively. Our work shows that bilayer tetragonal AlN nanosheets are promising catalysts for Li-O2 batteries.

Development of a semi-empirical interatomic potential appropriate for the radiation defects in V-Ti-Ta-Nb high-entropy alloy.

High-entropy alloys (HEAs) hold promise as candidate structural materials in future nuclear energy systems. Body-centred cubic V-Ti-Ta-Nb HEAs have received extensive attention due to their excellent mechanical properties. In this work, the Finnis-Sinclair interatomic potential for quaternary V-Ti-Ta-Nb HEAs has been fitted based on the defect properties obtained with the density functional theory (DFT) calculations. The new potential for Nb accurately reproduces the vacancy formation energy, vacancy migration energy and interstitial formation energy. The typical radiation defect properties predicted by the alloy potential were consistent with the DFT results, including the binding energies between substitutional solute atoms, the binding energy between substitutional atoms and vacancies, and the formation energy of interstitial solute atoms. In addition, the mixing enthalpies of the alloys were also consistent with the DFT results. The present potential can also describe reasonably the collision cascade process of quaternary V-Ti-Ta-Nb HEAs.

Theoretically evaluating two-dimensional tetragonal Si2Se2 and SiSe2 nanosheets as anode materials for alkali metal-ion batteries.

In this work, based on first-principles calculations, we theoretically predict two kinds of two-dimensional tetragonal Si-Se compounds, Si2Se2 and SiSe2, as the anode materials for alkali metal-ion batteries. The results show that Si2Se2 and SiSe2 are thermally and dynamically stable and have good electronic conductivity. The diffusion barriers of Li, Na and K atoms are 0.07 eV, 0.17 eV and 0.17 eV on the surface of Si2Se2, and 0.45 eV, 0.43 eV and 0.30 eV on the surface of SiSe2, respectively, which indicate excellent rate capability. Most remarkably, Si2Se2 and SiSe2 can deliver high specific capacities. The predicted specific capacities of Si2Se2 are 1252 mA h g-1, 501 mA h g-1 and 250 mA h g-1 for Li, Na and K storage, respectively, and the corresponding specific capacities of SiSe2 are 1441 mA h g-1, 865 mA h g-1 and 180 mA h g-1. In addition, the highest plateaus of open-circuit voltages are 0.50 V vs. Li+/Li, 0.60 V vs. Na+/Na and 1.01 V vs. K+/K for Si2Se2, and 1.13 V vs. Li+/Li, 1.09 V vs. Na+/Na and 1.01 V vs. K+/K for SiSe2, which are beneficial for achieving the high discharge voltage in full cells. Considering these advantages, Si2Se2 and SiSe2 monolayers can be competitive candidates as anode materials for alkali metal-ion batteries.

Synergistic engineering of shell thickness and core ordering to boost the oxygen reduction performance.

When benchmarked against the extended Pt(111), slightly weaker adsorption and stronger cohesion properties of surface Pt are required to improve activity and durability for the oxygen reduction reaction, respectively, making it challenging to meet both requirements on one surface. Here, using Pt(111) over-layers stressed and modified by Pt-TM (TM = Fe, Co, Ni, V, Cu, Ag, and Pd) intermetallics as examples, we theoretically identified ten promising catalysts by synergistically tailoring the skin thickness and substrate chemical ordering to simultaneously achieve weak adsorption and strong cohesion. More specifically, compared with Pt(111), all candidates exhibit 10-fold enhanced activity, half of which show improved durability, such as mono-layer skin on L12-Pt3Co or Pt3Fe, double-layer Pt on L13-Pt3Ni or Pt3Cu, and triple-layer skin on L11-PtCu, while double- or triple-layer skin on L10-PtCo or PtNi and double-layer skin on L12-PtFe3 show slightly poor durability. Although L10 and L12 based nanocrystals have been demonstrated extensively as outstanding catalysts, L11 and L13 ones hold great application potential. The coexistence of high activity and durability on the same surface is because of the different responses of surface adsorption and cohesion properties to the strain effects and ligand effects. When intermetallic-core@Pt-shell nanocrystals are constructed using this slab model, the necessity of protecting or eliminating low-coordinated Pt and the possibility of maximizing Pt(111) facets and core ordering by morphology engineering were highlighted. The current discovery provides a new paradigm toward the rational design of promising cathodic catalysts.

Shock-induced plasticity and phase transformation in single crystal magnesium: an interatomic potential and non-equilibrium molecular dynamics simulations.

An effective and reliable Finnis-Sinclair (FS) type potential is developed for large-scale molecular dynamics (MD) simulations of plasticity and phase transition of magnesium (Mg) single crystals under high-pressure shock loading. The shock-wave profiles exhibit a split elastic-inelastic wave in the [0001]HCPshock orientation and a three-wave structure in the [10-10]HCPand [-12-10]HCPdirections, namely, an elastic precursor, a followed plastic front, and a phase-transition front. The shock Hugoniot of the particle velocity (Up) vs the shock velocity (Us) of Mg single crystals in three shock directions under low shock strength reveals apparent anisotropy, which vanishes with increasing shock strength. For the [0001]HCPshock direction, the amorphization caused by strong atomic strain plays an important role in the phase transition and allows for the phase transition from an isotropic stressed state to the product phase. The reorientation in the shock directions [10-10]HCPand [-12-10]HCP, as the primary plasticity deformation, leads to the compressed hexagonal close-packed (HCP) phase and reduces the phase-transition threshold pressure. The phase-transition pathway in the shock direction [0001]HCPincludes a preferential contraction strain along the [0001]HCPdirection, a tension along [-12-10]HCPdirection, an effective contraction and shear along the [10-10]HCPdirection. For the [10-10]HCPand [-12-10]HCPshock directions, the phase-transition pathway consists of two steps: a reorientation and the subsequent transition from the reorientation hexagonal close-packed phase (RHCP) to the body-centered cubic (BCC). The orientation relationships between HCP and BCC are (0001)HCP⟨-12-10⟩HCP// {110}BCC⟨001⟩BCC. Due to different slipping directions during the phase transition, three variants of the product phase are observed in the shocked samples, accompanied by three kinds of typical coherent twin-grain boundaries between the variants. The results indicate that the highly concentrated shear stress leads to the crystal lattice instability in the elastic precursor, and the plasticity or the phase transition relaxed the shear stress.

Unraveling TM Migration Mechanisms in LiNi1/3Mn1/3Co1/3O2 by Modeling and Experimental Studies.

Electrochemical cycling induces transition-metal (TM) ion migration and oxygen vacancy formation in layered transition-metal oxides, thus causing performance decay. Here, a combination of ab initio calculations and atomic level imaging is used to explore the TM migration mechanisms in LiNi1/3Mn1/3Co1/3O2 (NMC333). For the bulk model, TM/Li exchange is an favorable energy pathway for TM migration. For the surface region with the presence of oxygen vacancies, TM condensation via substitution of Li vacancies (TMsub) deciphers the frequently observed TM segregation phenomena in the surface region. Ni migrates much more easily in both the bulk and surface regions, highlighting the critical role of Ni in stabilizing layered cathodes. Moreover, once TM ions migrate to the Li layer, it is easier for TM ions to diffuse and form a TM-enriched surface layer. The present study provides vital insights into the potential paths to tailor layered cathodes with a high structural stability and superior performance.

Wire-in-Wire TiO2/C Nanofibers Free-Standing Anodes for Li-Ion and K-Ion Batteries with Long Cycling Stability and High Capacity.

Wearable and portable mobile phones play a critical role in the market, and one of the key technologies is the flexible electrode with high specific capacity and excellent mechanical flexibility. Herein, a wire-in-wire TiO2/C nanofibers (TiO2 ww/CN) film is synthesized via electrospinning with selenium as a structural inducer. The interconnected carbon network and unique wire-in-wire nanostructure cannot only improve electronic conductivity and induce effective charge transports, but also bring a superior mechanic flexibility. Ultimately, TiO2 ww/CN film shows outstanding electrochemical performance as free-standing electrodes in Li/K ion batteries. It shows a discharge capacity as high as 303 mAh g-1 at 5 A g-1 after 6000 cycles in Li half-cells, and the unique structure is well-reserved after long-term cycling. Moreover, even TiO2 has a large diffusion barrier of K+, TiO2 ww/CN film demonstrates excellent performance (259 mAh g-1 at 0.05 A g-1 after 1000 cycles) in K half-cells owing to extraordinary pseudocapacitive contribution. The Li/K full cells consisted of TiO2 ww/CN film anode and LiFePO4/Perylene-3,4,9,10-tetracarboxylic dianhydride cathode possess outstanding cycling stability and demonstrate practical application from lighting at least 19 LEDs. It is, therefore, expected that this material will find broad applications in portable and wearable Li/K-ion batteries.

Electroreduction of Carbon Dioxide Driven by the Intrinsic Defects in the Carbon Plane of a Single Fe-N4 Site.

Manipulating the in-plane defects of metal-nitrogen-carbon catalysts to regulate the electroreduction reaction of CO2 (CO2 RR) remains a challenging task. Here, it is demonstrated that the activity of the intrinsic carbon defects can be dramatically improved through coupling with single-atom Fe-N4 sites. The resulting catalyst delivers a maximum CO Faradaic efficiency of 90% and a CO partial current density of 33 mA cm-2 in 0.1 m KHCO3. The remarkable enhancements are maintained in concentrated electrolyte, endowing a rechargeable Zn-CO2 battery with a high CO selectivity of 86.5% at 5 mA cm-2 . Further analysis suggests that the intrinsic defect is the active sites for CO2 RR, instead of the Fe-N4 center. Density functional theory calculations reveal that the Fe-N4 coupled intrinsic defect exhibits a reduced energy barrier for CO2 RR and suppresses the hydrogen evolution activity. The high intrinsic activity, coupled with fast electron-transfer capability and abundant exposed active sites, induces excellent electrocatalytic performance.

Boosting the charge transfer of Li2TiSiO5 using nitrogen-doped carbon nanofibers: towards high-rate, long-life lithium-ion batteries.

Li2TiSiO5 (LTSO) has a theoretical specific capacity of up to 315 mA h g-1 with a suitable working potential (0.28 V vs. Li/Li+). However, the electronic structure of Li2TiSiO5 is firstly investigated by theoretical calculation based on the first-principles approach, and the results demonstrate that Li2TiSiO5 acts as the insulator for transferring electrons. Therefore, the framework with better conductivity is very essential for Li2TiSiO5 to enhance the charge transfer kinetics. Nitrogen-doped carbon encapsulated Li2TiSiO5 nanofibers (LTSO/NDC nanofibers) are obtained by using carbamide as a nitrogen source through an electrospinning technique. The nitrogen-doped carbon matrix with high electronic conductivity improves the electrochemical properties of LTSO significantly. The diffusion coefficient of lithium ions (DLi+) is greatly improved by manual calculation. The LTSO/NDC nanofiber electrode can deliver 371.7 mA h g-1 at 0.1 A g-1 and 361.1 mA h g-1 at 0.2 A g-1, and also shows a comparable cycle performance which could endure a long cycle over 800 cycles at 0.5 A g-1 almost without capacity decay. Hence, the LTSO/NDC nanofiber anode with a high rate and a long life provides a new direction for the realization of LTSO-based compounds in lithium ion batteries.

New Insight into the Confinement Effect of Microporous Carbon in Li/Se Battery Chemistry: A Cathode with Enhanced Conductivity.

Embedding the fragmented selenium into the micropores of carbon host has been regarded as an effective strategy to change the Li-Se chemistry by a solid-solid mechanism, thereby enabling an excellent cycling stability in Li-Se batteries using carbonate electrolyte. However, the effect of spatial confinement by micropores in the electrochemical behavior of carbon/selenium materials remains ambiguous. A comparative study of using both microporous (MiC) and mesoporous carbons (MeC) with narrow pore size distribution as selenium hosts is herein reported. Systematic investigations reveal that the high Se utilization rate and better electrode kinetics of MiC/Se cathode than MeC/Se cathode may originate from both its improved Li+ and electronic conductivities. The small pore size (<1.35 nm) of the carbon matrices not only facilitates the formation of a compact and robust solid-electrolyte interface (SEI) with low interfacial resistance on cathode, but also alters the insulating nature of Li2 Se due to the emergence of itinerant electrons. By comparing the electrochemical behavior of MiC/Se cathode and the matching relationship between the diameter of pores and the dimension of solvent molecules in carbonate, ether, and solvate ionic liquid electrolyte, the key role of SEI film in the operation of C/Se cathode by quasi-solid-solid mechanism is also highlighted.

Dielectric Polarization in Inverse Spinel-Structured Mg2 TiO4 Coating to Suppress Oxygen Evolution of Li-Rich Cathode Materials.

High-energy Li-rich layered cathode materials (≈900 Wh kg-1 ) suffer from severe capacity and voltage decay during cycling, which is associated with layered-to-spinel phase transition and oxygen redox reaction. Current efforts mainly focus on surface modification to suppress this unwanted structural transformation. However, the true challenge probably originates from the continuous oxygen release upon charging. Here, the usage of dielectric polarization in surface coating to suppress the oxygen evolution of Li-rich material is reported, using Mg2 TiO4 as a proof-of-concept material. The creation of a reverse electric field in surface layers effectively restrains the outward migration of bulk oxygen anions. Meanwhile, high oxygen-affinity elements of Mg and Ti well stabilize the surface oxygen of Li-rich material via enhancing the energy barrier for oxygen release reaction, verified by density functional theory simulation. Benefited from these, the modified Li-rich electrode exhibits an impressive cyclability with a high capacity retention of ≈81% even after 700 cycles at 2 C (≈0.5 A g-1 ), far superior to ≈44% of the unmodified counterpart. In addition, Mg2 TiO4 coating greatly mitigates the voltage decay of Li-rich material with the degradation rate reduced by ≈65%. This work proposes new insights into manipulating surface chemistry of electrode materials to control oxygen activity for high-energy-density rechargeable batteries.

Dopant Segregation Boosting High-Voltage Cyclability of Layered Cathode for Sodium Ion Batteries.

As a widely used approach to modify a material's bulk properties, doping can effectively improve electrochemical properties and structural stability of various cathodes for rechargeable batteries, which usually empirically favors a uniform distribution of dopants. It is reported that dopant aggregation effectively boosts the cyclability of a Mg-doped P2-type layered cathode (Na0.67 Ni0.33 Mn0.67 O2 ). Experimental characterization and calculation consistently reveal that randomly distributed Mg dopants tend to segregate into the Na-layer during high-voltage cycling, leading to the formation of high-density precipitates. Intriguingly, such Mg-enriched precipitates, acting as 3D network pillars, can further enhance a material's mechanical strength, suppress cracking, and consequently benefit cyclability. This work not only deepens the understanding on dopant evolution but also offers a conceptually new approach by utilizing precipitation strengthening design to counter cracking related degradation and improve high-voltage cyclability of layered cathodes.

Molecular dynamics simulations of shock loading of nearly fully dense granular Ni-Al composites.

We used molecular dynamics simulations to study the shock propagation, inhomogeneous deformation, and initiation of the chemical reaction characteristics of nearly fully dense reactive Ni-Al composites. For shocks with piston velocities Up ≤ 2.0 km s-1, particle velocity dispersion was observed at the shock front, which increased on increasing the shock strength. Plastic deformation mainly occurred at the grain boundaries or grain junction during the shock rise and was accompanied by the generation of a potential hot spot in the region where severe plasticity happens. The composite exhibited higher strength and lower reactivity than the mixtures with certain porosity. In addition, the shock-induced premature melting of Al led to the expansion of particle velocity dispersion from the wavefront to the shocked zone and the formation of a heterogeneous velocity field for stronger shocks beyond critical Up (2.5 km s-1). The velocity heterogeneity in the shocked region led to localized shear, strong erosion of Ni, and occurrence of ultrafast chemical reactions. Therefore, the shock-induced premature melting of Al led to the mechanochemical effect and played a role in the shock-induced chemical reaction in the reactive metal system.

miR-1249-3p accelerates the malignancy phenotype of hepatocellular carcinoma by directly targeting HNRNPK.

BACKGROUND: microRNAs (miRNAs) have been implicated to play crucial roles in carcinogenesis. miR-1249-3p was reported to be abnormally expressed in multiple human cancers. However, its biological role and the associated underlying mechanisms in hepatocellular carcinoma (HCC) remain largely unknown. METHODS: miR-1249-3p expression level in HCC cell lines and normal cell line was measured by quantitative real-time PCR. Role of miR-1249-3p on HCC cell proliferation, colony formation, and invasion was examined by cell counting kit-8 assay, colony formation assay, and transwell invasion assay, respectively. Luciferase activity reporter assay and western blot were performed to validate whether heterogeneous nuclear ribonucleoprotein K (HNRNPK) was a direct target of miR-1249-3p. Effect of miR-1249-3p on overall survival of HCC patients was analyzed at KM Plotter website. RESULTS: We found miR-1249-3p expression level was increased, while HNRNPK expression level was decreased in HCC cell lines compared with normal cell line. Knockdown miR-1249-3p expression inhibits HCC cell proliferation, colony formation, and cell invasion through regulating HNRNPK in vitro. We also showed high miR-1249-3p expression was a predictor for poor overall survival of HCC patients. CONCLUSIONS: These findings about miR-1249-3p/HNRNPK pair provide a novel therapeutic method for HCC patients.

Intrinsic strain-induced segregation in multiply twinned Cu-Pt icosahedra.

We present an atomistic simulation study on the compositional arrangements throughout Cu-Pt icosahedra, with a specific focus on the effects of inherent strain on general segregation trends. The coexistence of radial and site-selective segregation patterns is found in bimetallic nanoparticles for a broad range of sizes and compositions, consistent with prior analytical and atomistic models. Through a thorough comparison between the composition patterns and strain-related patterns, it is suggested that the presence of gradient and site-selective segregation is natural to largely relieve the inherent strain by preferential segregation of big atoms at tensile sites and vice versa, as previously hypothesized in the literature. Analogous to the case of single crystal particles, Cu-rich surface and damped oscillations can also be found in the outer shells of icosahedra, which are dominated by the lowering of both the surface energy and the chemical energy. The thermodynamic stability of segregated icosahedra is similar to segregated cuboctahedra but higher than disordered bulk alloys, validating prior thinking that element segregation driven by strain relief can extend the stability range of multiply-twinned nanoparticles. Our work sheds new light on understanding strain-induced segregation in multiply-twinned nanosystems that have elements with large lattice mismatch and strong alloying ability.