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This paper presents a multi-scale numerical method to study the electrolyte material BaZrO3 (BZO) and gives numerical implementations and results. At the microscopic level, molecular dynamics (MD) is used to model the atomic structure of BZO. At the macroscopic level, the finite element method is used for loading and numerical solution. To bridge the microscopic and macroscopic scales, the concept of coarse-grained and coupled algorithms was used to establish a relationship between the atomic mass and the number of nodes in a continuous medium by means of a weighted residual method. This approach takes into account the anisotropy of the atomic structure of BZO and determines an intrinsic nature law through detailed modelling of the microstructure. We first describe the principle of the Atom-to-Continuum (AtC) multiscale approach and verify the accuracy of the multiscale calculation method by comparing the stress–strain curves of BZO with a central crack under the AtC method and MD simulations. The mechanical response of the crack under macroscopic and microscopic calculations is then observed and discussed by combining it with finite element software. Under the finite element simulations, the crack extends forward in a cleavage manner, while in the MD simulations the results show a clear directional dependence: the (100) surface fracture involves in-plane slip, with the crack propagating forward perpendicular to the plane between Zr and O; in the (110) surface the crack is unstable as it extends, resulting in a zigzag crack extension path, with the final crack remaining in the same direction as the initial direction remains the same. Our study not only reveals the fracture mechanism of perovskite oxide BZO but also presents a multi-scale approach that allows for large-scale calculations, providing a new way of studying the material design and applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel strategy of bimetallic MOFs for enhanced PAAS is designed. • The enhanced PAAS is ascribed to the improved mass transfer in MOFs. • Sustainable NH 3 production rate achieves 77.5 μmol g−1·min−1 in 36 h or ∼ 30 cycles. • Hypothetical zero-carbon ammonia plant exhibits notable competitiveness. Plasma-assisted ammonia synthesis (PAAS) can produce ammonia using highly energetic, electronically excited nitrogen and Hydrogen radicals at low temperatures and atmospheric pressure, which has been regarded as a prospective alternative to the Haber − Bosch process. PAAS can exclusively use renewable power (solar, wind, etc.) to achieve green, decentralized and efficient ammonia synthesis. However, current catalysts for PAAS are suffering from low efficiency, poor stability and cyclability. Herein, we demonstrate a one-step hydrothermal synthesis of Ni-Co bimetallic metal–organic frameworks (MOFs) for PAAS. Attributed to the amplified gas transport capability and bimetallic coupling, the Ni-Co-MOF exhibits significantly improved PAAS performance: 88.21 μmol g−1·min−1, above 30 % increase over 5 wt% Ni/Al 2 O 3. The high stability of Ni-Co-MOF under the harsh electric field enables its durable performance (36 h) and excellent cyclability (24 cycles). Finally, to determine the viability of PAAS for industrial applications, we construct a hypothetical zero-carbon ammonia plant using only renewable energy sources, and the outcomes indicate that PAAS has significant competitiveness for future ammonia production. [ABSTRACT FROM AUTHOR]

We develop a multiscale framework capturing the primary interaction, displacement cascade generation and evolution, and realistic observable damaged structure based on Monte Carlo, Molecular Dynamics, and Object Kinetic Monte Carlo using an effective defect information transmitting scheme. The radiation effects of phosphorus-doped n-type silicon materials are simulated based on a multiscale framework, and the results are consistent with experimental observations. The simulation results show that, the incident particle type has a large effect on the concentrations and distribution of defects, which is closely related to the Primary Knock-On Atom (PKA) energy spectra and the defects evolution of defects. A negative correlation between defect concentration and fluence rate is attributed to the dissipation of subsequent PKA kinetic energy in the pre-cascade region. By comparing the interatomic bond length, we reveal that the doped atom can change displacement threshold energy, thereby affecting the defect concentration. [ABSTRACT FROM AUTHOR]

Summary: In this paper, the strain effects on the energy barrier of proton diffusion in Y‐doped BaCeO3 (BCY) and Y‐doped BaZrO3 (BZY) are investigated by detailed density functional theory calculations. The energy barrier of proton rotation decreases when the tensile strain is applied. For intra‐octahedral proton transfer, the energy barrier decreases when the tensile strain is applied while for inter‐octahedral proton transfer the energy barrier increases when the tensile strain is applied. However, we found that for intra‐octahedral proton transfer the energy barrier of BZY shows the opposite strain effect. To understand the underlying mechanism behind this opposite trend we decomposed proton diffusion into three elementary steps and the opposite trend of the energy barrier of BCY and BZY during intra‐octahedral proton transfer is pinpointed to the opposite bond order change of the hydrogen bond. In all, we explored the strain effects on the energy barrier of proton diffusion in BCY and BZY from a microscopic perspective, showing the potential to tune the energy barrier of proton transport in perovskite oxide with strain engineering and thus design novel proton conductors. [ABSTRACT FROM AUTHOR]

Kinetic Monte Carlo (KMC) simulations have been used for electron beam physical vapor deposition (EB‐PVD) of ZrO2 coatings, with the critical potential function fitted by full first‐principles calculations in the framework of density functional theory, emphasizing the effect of critical processing parameters, for example, the substrate temperature (600–1150 K), deposition rate (0.03–7.5 μm/min), and initial kinetic energy (0–0.5 eV). Here, the interaction between ZrO2 particles is described by coarse grain (CG) model with a numerical non‐bonded potential developed by multi‐iterative boltzmann inversion (multi‐IBI). Overall, the calculated energy barrier by the nudged elastic band (NEB) shows the internal diffusion (3.29–4.80 eV) requires more energy than the surface diffusion (2.90–3.42 eV), because of fewer surrounding particles in the latter. Moreover, the energy barrier of Line Jump is smaller than that of Schwoebel Jump, contributing to the columnar grains rather than a dense coating. Of importance, the simulated morphologies of ZrO2 coatings are well consistent to experiments, with a weaker effect from the substrate temperature, initial kinetic energy to deposition rate. Furthermore, the porosity can be effectively reduced by increasing the temperature and initial kinetic energy, however, with a slight increase when increasing the deposition rate. [ABSTRACT FROM AUTHOR]

[Display omitted] • A machine learning potential is developed to perform MD simulation with DFT accuracy. • The mechanical properties of BZO with various Y-doping concentrations were compared. • The mechanical properties of BZY with various levels of hydration were compared. • The mechanical properties of BZY and hydrated BZY were compared. The hydration reaction leads to non-uniform stresses and strains inside solid oxide electrolytes, which seriously affects the mechanical properties of the material. Machine learning (ML) molecular dynamics (MD) provides an excellent means to investigate the effects of hydration on the structural and mechanical properties of electrolytes. In this paper, we develop an excellent ML potential with the accuracy of near first principles calculations and the efficiency of classical MD simulations to study the doping and hydration of BaZrO 3 (BZO) materials. The lattice constants, elastic constants, thermal expansion coefficients (TEC) and melting point of BZO and the enthalpy of hydration of Y doped BaZrO 3 (BZY) were calculated, and the results agree with the density functional theory (DFT) reference data, validating the accuracy of the ML potential. The study of the mechanical properties of BZY after the occurrence of the hydration reaction reveals that the Young's modulus and strength decrease significantly with the increase of the Y doping concentration, and the main reason for this decrease is the creation of oxygen vacancies by the doping process, which reduce the number of chemical bonds. The increase in hydration level also causes a decrease in the Young's modulus and strength, which is mainly attributed to the chemical expansion and weakening of the chemical bonds caused by protonic defects. Finally, the changes in Young's modulus and strength before and after hydration was also found to be only slightly different, indicating that the bond-strengthening effect induced by the filling of oxygen vacancies is compensated mainly by the bond-weakening due to protonic defects. The research results can contribute to understanding material design rules to rationalize the chemical expansion to optimize the chemical mechanical response of oxide ceramics, ultimately developing more stable proton conductors for proton based solid oxide fuel cells and electrolytic cells. [ABSTRACT FROM AUTHOR]

The acceptor-doped BaZrO 3 (BZY) shows considerable bulk proton conductivity. However, the higher grain boundary (GB) resistances significantly limit the overall transport of protons in polycrystalline samples. The fundamental questions about the proton diffusion mechanism at the defects are still unclear. By performing detailed density functional theory (DFT) calculations, we have studied the diffusion properties of protons in GB, where the presence of large free space and hydrogen bond leads to a significant proton trapping in GB structure. By comparing the characteristics of proton diffusion in BZY and BZY-GB, we found that in both structures, the local lattice deformation is important in both the proton rotation and transfer steps involved in proton diffusion. By calculating the change in bond strength, the decrease of A ions during the proton rotation process in GB leads to a significant change in the bond strength of the remaining O and A ions, and for the increase in the number of oxygen donor and B ion interaction bonds during the proton transfer process in GB, both of which increase the energy barrier for local lattice deformation such as O–B rotational motion, thus inhibiting the proton diffusion in GB. Our results give mechanical insights into the high resistance to proton diffusion in GB, clarifying the sources of energy barriers for proton diffusion in GB, and lay the foundation for industrial applications of proton conductors. [ABSTRACT FROM AUTHOR]

The complex operating environment severely tests the mechanical stability of the electrolyte material BaZrO 3 (BZO), which affects the performance of solid oxide fuel cells(SOFCs). Molecular dynamics (MD) simulation provides an efficient method to research the mechanical behavior of nanocrystalline materials. In the interest of researching the mechanical behavior of BZO materials utilizing a machine learning (ML) MD approach, this article has established the most effective ML potential with DFT reliability. By contrasting the lattice constants and elastic constants with the DFT data, the precision of the potential was confirmed. By simulating the uniaxial tensile mechanical behavior of the BZO models without crack and with a central crack in the crystal orientation of [100] and [110], we found that the BZO material has a significant anisotropic property. In the crack-free model, the BZO crack propagation mode in the [100] crystal orientation is a shear fracture. The central microcrack tilts downward and expands symmetrically in the [110] crystal-oriented BZO model. When the initial structure with a central crack, the fracture mode changes significantly, and in both crystal orientations, the crack fracture along the Ba O plane, the crack expands horizontally in the BZO model in the [100] crystal orientation and the crack expands zigzag in the BZO model in the [110] crystal orientation. The calculations of fracture strength, critical energy release rate, and fracture toughness show that the [110] crystal-oriented BZO has a stronger resistance to fracture than the [100] crystal-oriented BZO model. • A machine-learning potential is developed to perform MD calculations with DFT accuracy. • Fracture mechanical behavior of BaZrO 3 with and without central cracking was compared for different crystal orientations. • Fracture parameters were calculated using ML potentials to compare fracture resistance of different BaZrO3 structures. [ABSTRACT FROM AUTHOR]

Abstract In this paper, a new interionic potential is derived for silver iodide (AgI) via the Chen-Möbius lattice inversion and ab initio calculation. The accuracy of the proposed potential is checked by comparing the molecular dynamics simulation results on the static properties, structural stability, disordered states, mean-squared displacement and phase transition of AgI with experimental data. The simulation results are consistent with experimental data and density functional theory (DFT) calculations, indicating that the proposed interionic potential is valid over a wide range of interionic separations and applicable for describing the major properties of AgI. Highlights • We derive a new interionic potential for AgI via the Chen-Möbius lattice inversion and DFT calculations. • The accuracy of the proposed potential is checked by comparing the MD simulation results with experimental and DFT data. • The potential developed in this work is more favorable in describing several properties than former potential. [ABSTRACT FROM AUTHOR]

CO is a main component of syngas, which can be produced from the gasification of organic wastes and biomass. CO can be converted to methane by anaerobic digestion (AD), however, it is still challenging due to its toxicity to microorganisms and limited knowledge about CO converting microorganisms. In the present study, anaerobic granular sludge (AGS) was used for the simultaneous biomethanation of wastewater and CO. Batch experiments showed that AGS tolerated CO partial pressure as high as 0.5 atm without affecting its ability for synthetic wastewater degradation, which had higher tolerance of CO compared to suspended sludge (less than 0.25 atm) as previously reported. Continuous experiments in upflow anaerobic sludge blanket (UASB) reactors showed AGS could efficiently convert synthetic wastewater and CO into methane by applying gas-recirculation. The addition of CO to UASB reactor enhanced the hydrogenotrophic CO-oxidizing pathway, resulted in the increase of extracellular polymeric substances, changed the morphology of AGS and significantly altered the microbial community compositions of AGS. The microbial species relating with CO conversion and their functions were revealed by metagenomic analysis. It showed that 23 of the 70 reconstructed genome bins (GBs), most of which were not previously characterized at genomic level, were enriched and contained genes involved in CO conversion upon CO addition. CO-converting microorganisms might be taxonomically more diverse than previously known and have multi-functions in the AD process. The reductive tricarboxylic acid (TCA) cycle in combination with the oxidation of the CO was probably crucial for CO utilization by the majority of the GBs in the present study. [ABSTRACT FROM AUTHOR]

The mechanical properties of two-dimensional (2D) interlinked carbon nanotube (CNT) network are investigated using ab initio calculation and molecular dynamics simulations (MD) with Reaxff force field. The simulation results show that bulk 2D interlinked CNT network has good mechanical properties along the axial direction which can be comparable to that of single-walled CNT and graphene, but has better ductility along the radial direction than single-walled CNT and graphene. In addition, the mechanical properties of 2D interlinked CNT network ribbon along the radial direction depend strongly on the size of the ribbon. The Young's modulus and Poisson's ratio decrease as the size increases while the fracture strain increases with the size increasing. By analyzing the atomic structural (both bond length and atomic von Mises stress) evolution of the ribbons, the mechanism of a brittle-to-ductile transition is revealed. The exploration of the mechanical properties of the 2D interlinked CNT network paves the way for application of the relevant devices that can benefit from the high Young's modulus, high tensile strength, and good ductility. [ABSTRACT FROM AUTHOR]

Methanation of propionate requires syntrophic interaction of propionate-oxidizing bacteria and hydrogenotrophic methanogens, which is referred to as interspecies electron transfer. The present study showed that 10 mg/L conductive magnetite enhanced the methane production rate from propionate by around 44% in batch experiments, and both direct interspecies electron transfer and interspecies H 2 transfer were thermodynamically feasible with the addition of magnetite. The methanation of propionate facilitated by magnetite was also demonstrated in a long-term operated continuous reactor. The methane production rate from acetate by the enriched mixed culture with magnetite was higher than that without magnetite, while similar methane production rates were found from H 2 /CO 2 by the enriched mixed culture with and without magnetite. The ability to utilize molecular H 2 indicated interspecies H 2 transfer played a role in the enriched culture with magnetite, and propionate-oxidizing bacteria relating with interspecies H 2 transfer were also detected by metagenomic sequencing. Metagenomic sequencing analysis also showed that Thauera , possibly relating with direct interspecies electron transfer, were enriched with the addition of magnetite. iTRAQ quantitative proteomic analysis, which was used in mixed culture for the first time, showed that magnetite induced the changes of protein expression levels involved in various pathways during the methanation of propionate. The up-regulation of proteins involved in propionate metabolism were found, and they were mainly originated from propionate-oxidizing bacteria which were not reported to be capable of direct interspecies electron transfer until now. Cytochrome c oxidase was also revealed as the possible protein relating with direct interspecies electron transfer considering its up-regulation with the addition of magnetite and origination from Thauera . Most of the up-regulated proteins in methane metabolism were originated from Methanosaeta , while most of the enzymes with down-regulated proteins were originated from Methanosarcina . However, the up-regulated proteins relating with hydrogenotrophic methanogenesis were originated from neither Methanosaeta nor Methanosarcina , indicating they were not involved in direct interspecies electron transfer. The hydrogenotrophic methanogens, e.g. Methanospirillum , Methanosphaerula et al., might be involved in direct interspecies electron transfer. Overall, the present study showed that both direct interspecies electron transfer and interspecies H 2 transfer were present during methanation of propionate facilitated by magnetite. [ABSTRACT FROM AUTHOR]

The present study compared the mesophilic and thermophilic alkaline fermentation of waste activated sludge (WAS) for hydrogen production with focus on homoacetogenesis, which mediated the consumption of H 2 and CO 2 for acetate production. Batch experiments showed that hydrogen yield of WAS increased from 19.2 mL H 2 /gVSS at 37 °C and pH 10–80.1 mL H 2 /gVSS at 55 °C and pH 10. However, the production of volatile fatty acids (mainly acetate) was higher at 37 °C and pH 10 by comparison with 55 °C and pH 10. Hydrogen consumption due to homoacetogenesis was observed at 37 °C and pH 10 but not 55 °C and pH 10. Higher expression levels of genes relating with homoacetogenesis and lower expression levels of genes relating with hydrogen production were found at 37 °C and pH 10 compared to 55 °C and pH 10. The continuous experiment demonstrated the steady-state hydrogen yield of WAS was comparable to that obtained from batch experiments at 55 °C and pH 10, and homoacetogenesis was still inhibited. However, the steady-state hydrogen yield of WAS (6.5 mL H 2 /gVSS) was much lower than that (19.2 mL H 2 /gVSS) obtained from batch experiments at 37 °C and pH 10 due to the gradual enrichment of homoacetogens as demonstrated by qPCR analysis. The high-throughput sequencing analysis of 16S rRNA genes showed that the abundance of genus Clostridium , containing several homoacetogens, was 5 times higher at 37 °C and pH 10 than 55 °C and pH 10. [ABSTRACT FROM AUTHOR]

Graphyne, a two-dimensional planar carbon allotrope and consisting of sp and sp 2 carbon atoms, receives great attention in a wide community of scientists and engineers beyond graphene. Herewith we investigate the thermal transport property of graphyne and graphyne nanoribbons by performing nonequilibrium molecular dynamics simulation. Our simulations reveal abnormal thermal transport in graphyne that exhibits a low thermal conductivity (as low as 8 W/mK at room temperature), which is two to three orders of magnitude lower as compared to graphene. Detailed lattice dynamic calculations and phonon polarization analysis suggest that, the intrinsically low thermal conductivity of graphyne originates from the localization and the domination of the low frequency in-plan longitudinal modes to the acetylenic linkages and the large lattice vibration mismatch between the linkages and the hexagonal rings, which induces inefficient energy transfer between the soft phonon modes in the linkages and the stiffer vibrational modes in the hexagonal rings. We also illustrated an intriguing width dependent thermal conductivity of graphyne nanoribbons, which is fundamentally different from that of graphene nanoribbons and stems from the surface dominated phonon modes presented in the graphyne edge. Our simulations provide a detailed physical picture of thermal transport in graphyne and could offer useful guidance for engineering the thermal transport properties of graphyne for applications of graphyne related devices such as thermoelectrics. [ABSTRACT FROM AUTHOR]

Proton transport in perovskite oxides (ABO 3) is a complex dynamical process involving hydroxide ion rotation and proton transfer. Combining ab initio molecular dynamics (AIMD) and machine-learning molecular dynamics (MLMD) simulations of proton dynamics in Y-doped BaZrO 3 perovskite oxide, we systematically illustrate the anomalous characteristics of proton motion. At short times, proton performs superdiffusion through the O H wag and proton transfer. At intermediate times, the larger rotation angle results in the larger plateau value. At longer times, proton diffusion first becomes subdiffusive due to the hydroxide ion rotations then gradually turns to normal diffusion. A theoretical model is also offered to quantitatively describe this abnormal proton diffusion. In all, this work provides a more complete understanding of proton dynamics in perovskite oxides. • A machine-learning potential is developed to perform MD simulations with DFT accuracy. • The anomalous characteristics of proton motion in Y-doped BaZrO 3 are systematically illustrated at different time intervals. • A theoretical model is proposed to quantitatively describe the abnormal proton diffusion in Y-doped BaZrO 3. [ABSTRACT FROM AUTHOR]

Highlights: [•] The zigzag graphyne family structure displays semi-conductive characteristic. [•] The armchair graphyne family structure displays metallic characteristic. [•] With the length of C links increasing, the conductivity of graphyne family decreases. [•] The zigzag GNR-graphdiyne heterojunction shows superior rectification behavior. [Copyright &y& Elsevier]

The mechanical properties of silicene are investigated using ab initio calculation and molecular dynamics simulations with different empirical potentials. The simulation results show that the calculated Young's modulus of bulk silicene with EDIP model is consistent with the ab initio calculations. The chirality has a significant effect on the critical strain and stress of bulk silicene under uniaxial tension. In addition, the Young's modulus depends strongly on the chirality and size of the silicene nanoribbon due to the edge effects. The fracture process of a silicene nanoribbon is also studied. [ABSTRACT FROM AUTHOR]

Abstract: Molecular dynamics simulations are used to investigate the mechanical properties of a silicon nanofilm covered with a defective graphene. Our results show that graphene not only enhances the mechanical properties of a silicon nanofilm but also unifies the mechanical properties of the ultrathin silicon nanofilms among different crystal orientations. The Young''s modulus and critical stress of the silicon nanofilm along four crystal orientations covered with graphene decrease as the thickness of the silicon nanofilm increases. In addition, we study the effects of monoatomic vacancies and Stone–Wales (SW) defects with various concentrations on the mechanical properties of a silicon nanofilm covered with defective graphene. The results show that Young''s modulus reduces linearly for monoatomic vacancies and a relatively smaller dependence is observed on SW defects, while the critical stress is more sensitive to the presence of both types of defects. The results in this paper demonstrate the significance of graphene in enhancing the mechanical properties of the silicon nanofilm. [Copyright &y& Elsevier]

Nonequilibrium molecular dynamics (NEMD) is used to investigate the thermal-transport properties of a silicon nanofilm covered with graphene (Gr/Si/Gr nanofilm). The investigation results demonstrate that graphene can enhance the thermal-transport properties and weaken the ballistic characteristics of silicon nanofilm. Under the action of a small strain, the thermal conductivity decreases with the growth of tensile and compressive strain, respectively. In addition, the higher-frequency phonons in graphene give more contributions to the variation of thermal conductivity of Gr/Si/Gr nanofilm under strain. The thermal conductivity of Gr/Si/Gr nanofilm increases linearly with the increase of temperature in the lower-temperature regime due to the quantum effect, and begins to clearly decrease when the temperature exceeds a definite value. [ABSTRACT FROM AUTHOR]

Abstract: Molecular dynamics simulations are used to investigate the mechanical properties of a silicon nanofilm covered with graphene. Our results show that graphene can enhance the mechanical properties of a silicon nanofilm. The Young’s modulus of the silicon structure covered with graphene decreases as the thickness of the silicon nanofilm increases. We also investigate the fracture process of the silicon structure covered with graphene. The results in this paper suggest that silicon structures covered with graphene open up opportunities for design of micro and nanoelectromechanical systems. [Copyright &y& Elsevier]

Abstract: The nanomechanical properties of Si/a-Si core–shell NWs are investigated using molecular dynamics simulations with EDIP model. Under uniaxial compressive and tensile loading, the computed Young’s modulus increases as the radius of crystalline core increases and decreases as the thickness of amorphous shell increases. Whereas the critical strains are found to be independent of the size of crystalline cores and amorphous shells. For the nonaxial torsional and bending strains, both torsional stiffness and bending stiffness increase as the thickness of amorphous shell increases and also as the radius of crystalline core increases. In addition, the critical torsion angle rapidly decreases as the thickness of amorphous shells increases and also as the radius of crystalline core increases. However, the critical bending angles are independent of the size of crystalline cores and amorphous shells. These results show that the amorphous shell has significant effects on the mechanical properties of Si/a-Si core–shell NWs under external loadings. [Copyright &y& Elsevier]

Abstract: Molecular dynamics simulations are performed to investigate the interaction between 60° shuffle dislocation and tetrainterstitial (I 4) cluster in silicon, using Stillinger–Weber (SW) potential to calculate the interatomic forces. Based on Parrinello–Rahman method, shear stress is exerted on the model to move the dislocation. Simulation results show that the I 4 cluster can bend the dislocation line and delay the dislocation movement. During the course of intersection the dislocation line sections relatively far away from the I 4 cluster accelerate first, and then decelerate. The critical shear stress unpinning the 60° dislocation from the I 4 cluster decreases as the temperature increases in the models. [Copyright &y& Elsevier]

Abstract: Molecular dynamics simulations with Stillinger–Weber potential are used to study the buckling behavior of single-crystalline silicon nanowires under uniaxial compression. Nanowires with axial orientations along the [100], [110], [111], and [112] crystallographic directions, which correspond to experimentally synthesized nanowires, are studied. The effects of simulation temperature, strain rate, and wire length on the buckling behavior are investigated. The simulation results indicate that critical load clearly decreases with increasing temperature and with decreasing strain rate. Additionally, the present results show that the critical load decreases with the increase of wire length, which is in agreement with the Euler theory. [Copyright &y& Elsevier]

Abstract: The tensile and melting behaviours of single crystalline silicon nanowires (SiNWs) are studied using molecular dynamics simulations. The atomic interactions are described using the Stillinger–Weber potential. The tensile test results show that the tensile behaviour of the SiNWs is strongly dependent on the simulation temperature, strain rate, and diameter of the nanowires. The critical load clearly decreases with increasing temperature and with decreasing strain rate, and increases with increasing diameter. Additionally, the melting test results demonstrate that the melting temperature of the SiNWs decreases with decreasing diameter, due to the increase in surface energy. The structural transition of SiNWs with an increasing temperature is also studied. [Copyright &y& Elsevier]

The success of fabricating single layer graphene and silicon nanofilm (could be as thin as single layer so far) has triggered enormous interest in exploring their unique physics and novel applications. An intuitive idea is to investigate what happens if we construct a heterostructure composed of these two sheets. In this paper, we perform nonequilibrium molecular dynamics simulations to systematically investigate the in-plane thermal transport in graphene/silicon/graphene (Gr/Si/Gr) heterostructures. The effects of Si film thickness, interfacial interaction strength, and length on the thermal conductivity of the Gr/Si/Gr heterostructures are explicitly considered. Our simulations identify a unified scaling law for thickness dependence of thermal conductivity of the Gr/Si/Gr heterostructures, despite different interfacial interaction forms are used (weak van der Waals interaction and strong covalent bonding). By quantifying relative contribution from phonon polarizations and defining heat flux onto single atom, we reveal and fully understand the different mechanisms governing the phonon transport in the Gr/Si/Gr heterostructures for the two different interfacial interaction forms. We also found that the thermal conductivity of Gr/Si/Gr heterostructure is nonmonotonically dependent on the van der Waals interaction strength between graphene and Si, but monotonically dependent on the graphene-silicon covalent bonding strength. Moreover, length dependence study shows that phonon transport in Gr/Si/Gr heterostructure becomes diffusive at much shorter length as compared with single layer graphene and bilayer graphene. Comparing to single and double graphene layers, the thermal conductivity of the Gr/Si/Gr heterostructure can be reduced with more than one order of magnitude for very long structures. These results suggest that Gr/Si/Gr heterostructures are promising for nanoscale devices due to their unique thermal transport properties. [ABSTRACT FROM AUTHOR]

By performing detailed density functional theory (DFT) calculations, we investigate the effect of A ion vacancy on both hydroxide ion rotation and proton transfer in Y-doped BaZrO 3. We find that A ions reduce the barrier for proton diffusion in a perovskite oxide, demonstrating the significance of perovskite structures as proton conductors. Proton diffusion is understood as a two-step mechanism consisting of hydroxide ion rotation and proton transfer. In both steps, lattice deformations play an important role – specifically, the outward O-B-O bending and A ion motions are important for hydroxide ion rotation, and inward O-B-O bending facilitates proton transfer. By comparing the bond strength, we reveal that an A ion can reduce the bond strength of O and B ion, thereby reducing the energy barrier for local lattice deformation such as O-B-O bending motion, which facilitates both hydroxide ion rotation and proton transfer. Our analysis provides a detailed atomistic understanding of the role of A-site ion on proton diffusion in perovskite oxides. The study presented here not only indicates the advantage of perovskite oxides as proton conductors but also elucidates the origin of proton diffusion barrier which can pave the way for design of novel proton conductors. • The energy barriers of proton diffusion are decomposed. • The local lattice deformations play a significant role in proton diffusion. • The migration energies of proton diffusion near an A ion vacancy are large. • The A-site ion in a perovskite oxide can reduce the B-O bond strength. • The A-site ion in a perovskite oxide facilitate local lattice deformations. [ABSTRACT FROM AUTHOR]

Abstract Aliovalent cation-doped perovskite-type oxides (AB O 3) exhibit proton conductivity originating from the hydration of oxide ion vacancies, which is accompanied by structural deformation, i.e. chemical expansion. The chemical expansion may lead to failure in electrochemical devices, and thus it is necessary to understand the causes of this process at the atomic scale. In this study, the chemical expansion behaviors of Y-doped strontium cerate and zirconate were comparatively investigated. High-temperature X-ray diffraction (HT-XRD) and thermogravimetric analysis (TGA) revealed that the cerate exhibits larger chemical expansion. Density Functional Theory (DFT) calculations revealed that this tendency can be accounted for by the different atomic distribution of the Y dopant between the cerate and zirconate, which results in differences in the size of the oxide ion vacancies to be hydrated as well as different elastic character. Highlights • High temperature X-ray and thermogravimetric analysis show yttrium-doped strontium cerate has higher chemical expansion than zirconate by hydration • Density functional theory suggests that the chemical expansion coefficient is depending on the configuration of Y atoms. • Density functional theory also suggests that size of oxide ion vacancies differs by the Y-Y configurations. [ABSTRACT FROM AUTHOR]

Wide bandgap β-Ga2O3 is an ideal candidate material with broad application prospects for power electronic components in the future. Aiming at the application requirements of β-Ga2O3 in space photoelectric devices, this work studies the influence of 40 MeV Si ion irradiation on the microstructure and optical properties of β-Ga2O3 epi-wafers. Raman spectroscopy analysis confirms that Si ion irradiation destroys the symmetric stretching mode of tetrahedral–octahedral chains in β-Ga2O3 epi-wafers, and the obtained experimental evidence of irradiation leads to the enhanced defect density of VO and VGa–VO from x-ray photoelectron spectroscopy. Combined with first-principles calculations, we conclude that most configurations of VO and VGa–VO are likely non-radiative, leading to quenching of experimental photoluminescence intensity. Unraveling optical degradation mechanism and predicting the optical application of β-Ga2O3 devices in the space environment by combining ground irradiation experiments with first-principles calculations still be one of the focuses of research in the future. [ABSTRACT FROM AUTHOR]

In this work, a simple, controllable and mass-produced microcrack technique for stretchable strain sensors is presented. Specifically, the conductive layer (hydroxylated MWCNTs) and the flexible substrate (Ecoflex) of fiber strain flexible sensors are modified based on proton irradiation defect engineering. The evolution of defects in sensitive materials and the density of microcracks in flexible substrates are controlled by controlling the irradiation fluence during the irradiation process. In particular, when the irradiation fluence is 1 × 1014 p cm−2, the gauge factor (GF) of the fiber strain sensor is as high as 1274.8, and the response time and recovery time are reduced by 49.4% and 45.1%, respectively. At the same time, the microcracked structure does not fracture easily under a large strain, the maximum strain being 800%. In addition, fiber strain flexible sensors can also be used to detect biomechanical signals in different scenarios. This simple and efficient microcrack technique opens up a new prospect for the fabrication of high-performance stretchable strain sensors. [ABSTRACT FROM AUTHOR]

In the article by Yuhang Jing et al. (pp. 1505–1509), the chirality and size effects on the mechanical properties of silicene nanoribbons are investigated based on atomistic simulation. Compared with ab initio calculations, the EDIP model of bulk silicene gives a more accurate Young's modulus than other empirical potentials. The chirality has a signifi cant effect on the critical strain and stress of bulk silicene under uniaxial tension. In addition, compared to zigzag edge, the armchair edge is weaker and has bigger effects on the Young's modulus of silicene nanoribbons when the nanoribbon width is smaller, which results in signifi cantly size‐ and chirality‐dependent Young's modulus of silicene nanoribbons. The fracture process of a silicene nanoribbon shows that as the strain increases to a certain value, sliding occurs and many atoms rearrange in the neck region. The deformation mechanism of the shearing action is similar to that of silicon nanowire. After the formation of the neck, plastic deformations mainly happen through the reconstruction and rearrangement of the neck region. Further theoretical and experimental studies are needed to investigate the mechanical properties of this new two‐dimensional silicon nanomaterial. [ABSTRACT FROM AUTHOR]

Materials that emit in the near‐infrared (NIR) region are at the forefront of both research and industry, mainly due to their wide applications in national security, nondestructive bioimaging, long‐wave communications, and photothermal conversion for medical care. As a key member of the luminescent materials family, metal halide perovskites have been intensively demonstrated to emit light in ultraviolet and visible regions. However, NIR‐emitting perovskites suffer from severe limitations, such as low photoluminescence quantum yield and poor chemical/optical stability, thereby preventing them from practical applications. Herein, the synthesis and growth of Cs2MoCl6 and Cs2WCl6 perovskite single crystals with ultrahigh chemical and optical resistance to heat, moisture, polar solvents, and high‐energy radiation is reported. Upon ultraviolet or blue excitation, these lead‐free single crystals emit light beyond 1100 nm, the longest wavelength ever reported for perovskite hosts. Mechanistic studies indicate that self‐trapped excitons are responsible for the NIR emission. The authors fabricate optoelectronic devices using these single crystals and demonstrate their broad applications in noninvasive palm vein imaging, night vision, and nondestructive food analysis. These results may stimulate research in the development of high‐efficiency NIR perovskite phosphors for fast, accurate biometric identification and food inspection. [ABSTRACT FROM AUTHOR]

• A novel stepwise Li-mediated electrochemical nitrogen reduction (Li-NRR) was developed. • The decomposition of solid-electrolyte interphase was revealed by decoupling the continuous Li-NRR. • Zn exhibited fastest electron transfer and Li+ diffusion, demonstrating best Li-NRR performance. • The proportion of active lithium was demonstrated to influence the Faraday efficiency. • LiCl generated in protonation process was found to enhance the system stability and facilitate the recycling of lithium. The lithium-mediated electrochemical nitrogen reduction reaction (Li-NRR) is a sustainable route for green NH 3 synthesis. It accelerates the N 2 reduction by reacting the inert N ≡ N with active Li metal. However, the study on the mechanism of the Li-NRR process remains limited. Herein, a novel stepwise Li-NRR system is established to separately optimize the major steps of Li-NRR: lithium-ion reduction, lithium nitridation, and Li 3 N protonation. It is revealed that during the Solid Electrolyte Interface (SEI) decomposition, the carbon chains in organic species become shorter, and Li x BF y is converted to LiF, which is similar to the continuous Li-NRR. Contrary to the continuous Li-NRR, the O/C ratio decreases as the SEI decomposes due to the absence of ethanol. Commercial Cu, Ni, and Zn are employed as cathodes in the experiments at various currents. The highest Faraday efficiency of 33.2 % and ammonia yield rate of 1404.5 μg h−1 cm−2 are achieved on Zn electrode owing to its superior electron transfer and enhanced Li+ diffusion than those of Cu and Ni. The current has also been found to affect Faraday efficiency through the portion of active lithium in coulomb efficiency experiments. Moreover, the LiCl generated in protonation process is found to facilitate lithium cycling. [ABSTRACT FROM AUTHOR]

Chemical looping ammonia synthesis (CLAS) is promising to achieve decentralized ammonia synthesis under ambient pressure. Here, we develop a highly selective composite nitrogen carrier for efficient CLAS based on transition metals (TMs=Co, Ni, Fe) decorated chromium nitride (CrN). Systematic studies indicate that the pristine CrN is extremely inert: only 4.5% lattice nitrogen can be consumed in reacting with H 2 (700 °C, 1 bar). Upon loading cobalt, the composite nitrogen carrier achieves lattice nitrogen conversion of 50.7% and ammonia selectivity up to 98.1%. Furthermore, Co-CrN exhibits excellent CLAS performance, attaining an average ammonia production rate of 466.1 μmol g−1 h−1 in 12 chemical loopings, which is ∼10 times that of the pristine CrN. Theoretical calculations reveal that the nitrogen vacancies generated in hydrogenation play a crucial role as activation centers for N 2 fixation through a Mars–van Krevelen mechanism. This work provides a novel strategy to optimize nitrogen carriers for enhanced CLAS. [Display omitted] • CLAS mediated by Cr-based nitrogen carriers was reported for the first time. • Novel strategy in designing synergistic nitrogen carriers with dual active sites. • Controlled conversion rate of lattice-N by 50.7% and high NH 3 selectivity at 98.1%. • Sustainable NH 3 production rate achieved 466.1 μmol g−1 h−1 in more than 12 cycles. • Reduced reaction energy barrier was verified in DFT calculations. [ABSTRACT FROM AUTHOR]

Chemical looping ammonia production (CLAP) technology provides additional freedom for the optimization of operating conditions via the strategy of stepwise reactions, which is promising to achieve green ammonia synthesis under mild conditions. Mn-based nitrogen carriers are ideal redox materials by virtue of their moderate thermodynamic properties and abundant crystalline phases, but their performance of hydrogenation in CLAP is still limited by the low reactivity. Herein, a series of Ni-Mn-N composite nitrogen carriers with different Ni/Mn ratios were prepared, and the effect of Ni doping on the performance of NH 3 production was investigated at atmospheric pressure. The nitrogen carriers modified with low level of Ni (<20 wt%) showed high activity and selectivity of hydrogenation, and the effective conversion of lattice nitrogen in 80Mn20Ni-N reached 36.1% at 750 °C, which was 15.7% higher than the undoped 100Mn-N. The introduction of low level of Ni can simultaneously enhance the bulk migration and interfacial reaction of lattice nitrogen and achieve the optimal kinetic matching between the both processes, thus promoting the activity and selectivity of lattice nitrogen converted to NH 3. This study presents new insights into the design of composite nitrogen carriers to enhance ammonia production in CLAP. • Ni-Mn-N composite nitrogen carriers were developed for chemical looping ammonia production. • The activity and selectivity of hydrogenation can be promoted by low level of Ni doping. • Ni dopants enhanced the bulk migration and interfacial reaction of lattice N. • Low level of Ni can achieve the optimal kinetic matching between the both processes. [ABSTRACT FROM AUTHOR]

Solid oxide fuel cells (SOFCs) are in a complex mechanical-thermal-electrochemical multi-field coupling condition, and traditional calculation methods are difficult to study from different scales concurrently. In this paper, we use a multi-scale method to investigate the mechanical properties of ceria. This multi-scale method cannot only obtain the micro-processes such as pre-phase transformation, phase transformation, and fracture represented by molecular dynamics (MD) calculations, but also acquire the displacement and stress fields by the finite element method (FEM). A center-cracked model is used to study the crack propagation and stress distribution near the crack tip. In the [100] crystal orientation, a stress-induced martensitic phase transformation occurs near the crack tip, while the [111] crystal orientation shows the characteristics of brittle fracture of ceramic materials. The stress-strain relationship calculated by this multi-scale method compares well with the results of MD simulations, which attests to its accuracy. [ABSTRACT FROM AUTHOR]

Summary: Gadolinia‐doped ceria (GDC), as an electrolyte of solid oxide fuel cells, reduces its mechanical property when exposed to reducing conditions. In this paper, the anisotropic mechanical behavior of non‐stoichiometric GDC solid electrolytes is investigated by using the molecular dynamics (MD) method. It is found that the oxygen vacancies whether from doping Gd3+ ions or generating Ce3+ ions by reduction have a serious impact on the mechanical properties such as phase transformation and fracture strength. The defect‐dependent tensile strength is observed to be consistent with reported experimental measurements. Moreover, increasing temperature reduces the fracture strength. The influence of temperature on the critical nucleation stress and the fluorite phase strength is further analyzed. Beyond that, GDC undergoes volumetric expansion due to non‐stoichiometric effects. The linear chemical strain and coefficient of compositional expansion (CCE) are calculated and compared with the experimental results. [ABSTRACT FROM AUTHOR]

Gadolinia-doped ceria (GDC) is one of widely used electrolyte materials for solid oxide fuel cells (SOFCs) due to its high ionic conductivity. In this paper, we report the anisotropic mechanical behavior of GDC solid electrolytes under electromechanical coupling loading by molecular dynamics (MD) simulation. For pure CeO 2 , it is found that low electric field merely reduces the fracture strength while high electric field directly changes phase transformation behavior in the [100] and [110] crystal orientations. In the [111] crystal orientation, the increase of electric field lead to the synchronous elevation of fracture stress by weakening the electrostatic repulsion between adjacent oxygen ions. And the doping concentration and temperature are considered to investigate the fracture behavior with electric field loading. Moreover, significant improvement of electrolyte conductivity is obtained by loading electric field on GDC. This finding might be able to provide a reasonable insight to reduce operating temperature of SOFC system. [ABSTRACT FROM AUTHOR]

Nanostructured thermoelectric materials are promising for modulating physical properties to achieve high thermoelectric performance. In this paper, thermal transport properties of armchair/zigzag graphene superlattice nanoribbons (A/Z graphene SLNRs) are investigated by performing nonequilibrium molecular dynamics simulations. The target of the research is to realize low thermal conductivity by introducing single-vacancy point defects. Our simulations demonstrate that the thermal conductivity of A/Z graphene SLNRs depends nonmonotonically on periodic length. In addition, introducing single-vacancy point defects into the superlattice nanoribbons could decrease the phonon tunneling in superlattice nanoribbons, so that the thermal conductivity could be reduced further. Furthermore, a monotonic dependence of the thermal conductivity of A/Z graphene SLNRs with length of zigzag part in periodic length is discovered. This phenomenon is explained by performing phonon property analysis. Our simulations deliver a detailed phonon transport in A/Z graphene SLNRs and provide useful guidance on how to engineer the thermal transport properties of A/Z graphene SLNRs for applications of nanoribbon-related devices in thermoelectrics. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulations is used to investigate the mechanical properties of three‐dimensional (3D) graphene under uniaxial tensile loading. The results show that the tensile deformation of 3D graphene exhibits size dependence along both armchair and zigzag directions. By analyzing the atomic von Mises stress and structural evolution, compared to the 3D graphene with smaller in‐plane cell size, the larger 3D graphene exhibits two typical deformation events, i.e., transverse structural shrinkage and axial elastic deformation. The fracture stress of 3D graphene is much smaller than that of 2D graphene because of its porous structure. However, the fracture strain of 3D graphene is larger than that of 2D graphene due to the larger transverse structural shrinkage along both armchair and zigzag directions. Effects of temperature, strain rate, and thickness of 3D graphene on the tensile behavior is investigated. The simulation results indicate that the fracture stress and the fracture strain decrease with increasing temperature and with decreasing strain rate. However, the fracture stress and the fracture strain is not dependent on the thickness of 3D graphene. The results in this paper suggest that 3D graphene with higher stretchability tunable by in‐plane cell size can be promising multifunctional materials for many engineering applications. [ABSTRACT FROM AUTHOR]

[Display omitted] Harsh radiation environments cause displacement damages in semiconductor components, resulting in performance degradation. Molecular simulations provide a unique approach to study the dynamic processes of radiation-induced defect production, clustering, and evolution to design and reinforce novel semiconductor components. In this paper, we developed a more efficient machine learning (ML) potential with DFT accuracy to investigate the radiation damage in silicon material. The accuracy of the potential was verified by comparing the static properties, defect formation energy, and threshold displacement energy with experiments and DFT data. By simulating the excitation of a single PKA we found that with the ML potential PKA has an impact over a larger spatial area compared to the empirical potentials. Finally, by simulating multiple PKA excitations in sequence, we found that the first several excited PKAs produce an amorphous region. For the later excited PKAs, the energies are dissipated when they cross through the amorphous region, resulting in a 36% decrease in newly generated defects. [ABSTRACT FROM AUTHOR]

[Display omitted] • The reliability of DLTS simulation is confirmed by the nonlocal hybrid functional. • The electron–phonon coupling is included to describe the hot carrier nonradiative capture in the DLTS simulation. • The DLTS simulation is verified by the radiation experiments. Deep level transient spectroscopy (DLTS) is a crucial technique to characterize the defects in semiconductor devices. Within the framework of the state-of-the-art density functional theory (DFT), the simulation for experimental DLTS spectra is realized successfully with high accuracy and intrinsic physics in this work, of which the reliability is confirmed by nonlocal hybrid functional. The electron–phonon coupling is included to describe the thermal-activated behavior of the hot carrier nonradiative capture reflected by DLTS signal. In the case study, the divacancy in silicon is employed for the flow of DLTS calculation as a benchmark, of which the results are verified by our 40 MeV Si irradiation experiments on the NPN and PNP bipolar junction transistors and previous reports. The problem we can address is the identification of defect characterized in DLTS experiments. The realization of DLTS simulation would have a profound significance for understanding the underlying physics in experimental observations and be a powerful leverage to define defect nature in semiconductors. [ABSTRACT FROM AUTHOR]

In this work, electron irradiation as a novel and simple method was used to fabricate wearable strain sensors with high comprehensive performance. Hydroxylated multi-walled carbon nanotubes (hydroxylated MWCNTs) were uniformly adsorbed on ecoflex etched by hydrofluoric acid (HF). After electron irradiation, a large number of defects and functional groups were successfully introduced into the hydroxylated MWCNTs/ecoflex, leading to a flexible strain sensor with high comprehensive performance such as ultra-low detection limit, fast response, and wide sensing range. Compared with the unirradiated sensors, the irradiated sensors have an ultra-low detection limit of 0.01% and a wide strain range (the maximum strain of 800%), the maximum gauge factor is increased by 344%, and the response time and recovery time are reduced by 50% and 89.2% respectively. The sensors can be used for monitoring the weak physiological movements and large-scale human movements, which has great potential in health monitoring. The electron irradiation as an activate method can provide a way for mass fabrication of flexible sensors with high comprehensive performance such as ultra-low detection limit and wide sensing range. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: The thermal transport properties of single-crystalline nanowires (carbon nanowires (CNWs) and silicon nanowires (SiNWs)) covered with amorphous silicon shell are investigated by non-equilibrium molecular dynamics (NEMD). The thermal conductivity of SiNWs covered with amorphous silicon shell (Si/a-Si core–shell NWs) is obviously lower than that of single-crystalline SiNWs and it keeps approximately constant when the temperature exceeds a definite value for the diffusion properties of amorphous shell. It is quite different from that of single-crystalline SiNWs whose thermal conductivity decreases significantly for relatively higher temperature. Compared to single-crystalline SiNWs, Si/a-Si core–shell NWs express stronger non-propagation, diffusion thermal transport properties. The thermal transport properties of CNWs covered with amorphous silicon shell (C/a-Si core–shell NWs) are essentially similar to that of Si/a-Si core–shell NWs. It expresses stronger non-propagation, diffusion thermal transport properties and its thermal conductivity increases very little with the growth of length. However, its diffusion characteristics are weaker than that of Si/a-Si core–shell NWs. Generally speaking, the amorphous shell and amorphous/crystalline interface play a negative role to the thermal conductivities and an enhance role to the diffusion characteristics of single-crystalline nanowires, however, their degree of effect on different single-crystalline nanomaterials is different. [Copyright &y& Elsevier]

Using toponym data, population data, and night-time light data, we visualized the development index of the Yi, Wa, Zhuang, Naxi, Hani, and Dai ethnic groups on ArcGIS as well as the distribution of 25 ethnic minorities in the study area. First, we extracted the toponym data of 25 ethnic minorities in the study area, combined with night-time light data and the population proportion data of each ethnic group, then we obtained the development index of each ethnic group in the study area. We compared the development indexes of the Yi, Wa, Zhuang, Naxi, Hani, and Dai ethnic groups with higher development indexes. The results show that the Yi nationality's development index was the highest, reaching 28.86 (with two decimal places), and the Dai nationality's development index was the lowest (15.22). The areas with the highest minority development index were concentrated in the core area of the minority development, and the size varied with the minority's distance. According to the distribution of ethnic minorities, we found that the Yi ethnic group was distributed in almost the entire study area, while other ethnic minorities had obvious geographical distribution characteristics, and there were multiple ethnic minorities living together. This research is of great significance to the cultural protection of ethnic minorities, the development of ethnic minorities, and the remote sensing mapping of lights at night. [ABSTRACT FROM AUTHOR]

A novel s econd- o rder r educed h omogenization (SORH) approach is introduced for analyzing dynamic thermo-mechanical coupling problems in axisymmetric inelastic structures with periodic micro-configuration. The axisymmetric heterogeneous structures are periodically distributed in radial and axial directions and homogeneous distribution in circumferential directions. Firstly, the nonlinear coupled thermo-mechanical model is proposed, and the high-order nonlinear local problems, effective material parameters and the nonlinear homogenization equations are derived successively by the multiscale asymptotic expansion. Further, in order to reduce the large computational amount evaluated by the classical multiscale homogenization approach, the reduced-order nonlinear multiscale models and the corresponding finite-element algorithms are established in detail. The key features of the proposed approach are that an efficient reduced-model form based on transformation field analysis (TFA) to analyze nonlinear local cell problems is proposed and a nonlinear thermo-mechanical problem which considers the mutual coupling for the temperature and displacement fields is computed. In particular, a new SORH algorithm is proposed for investigating the axisymmetric inelastic structures. Finally, three typical numerical experiments are carried out, and the effectiveness and correctness of our presented algorithms in simulating and predicting the macroscopic behavior of the heterogeneous structures are confirmed. • A novel second-order reduced homogenization approach is developed. • Nonlinear axisymmetric structures with periodic configurations are considered. • An efficient reduced-order form for nonlinear unit cell problems is studied. • Thermo-mechanical coupling problems of axisymmetric structures are analyzed. • Three typical numerical examples are introduced to confirm the proposed approach. [ABSTRACT FROM AUTHOR]