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DFT analysis of Re-modified WSe2 monolayers for adsorption of CO, C2H2, and C2H4 再修饰 WSe2 单层吸附 CO、C2H2 和 C2H4 的 DFT 分析
IF 1.8 4区 材料科学 Q3 MATERIALS SCIENCE, MULTIDISCIPLINARY Pub Date : 2024-08-28 DOI: 10.1088/1361-651x/ad6fbe
Suman Sarkar, Papiya Debnath, Debashis De, Manash Chanda
The sensing performances of the Rhenium (Re) doped Tungsten Diselenide (WSe2) monolayer for detecting small gas molecules such as carbon monoxide (CO), acetylene (C2H2), and ethylene (C2H4) have been analyzed in this paper. Density functional theory and non-equilibrium Green’s function have been used to examine the electrical and geometric structures of re-adorned WSe2 monolayer when subjected to dissolved gas analysis gases in the transformer oil. Hence, the electrochemical characteristics like Band diagram and density of states are detailed. Adsorption systems’ recovery capabilities, Mulliken population, and adsorption energy have been examined to determine their stability. Studies also show that Re-doped WSe2 monolayer exerts deformation and as a result, the band gap narrowed down. At ambient temperature (273 K–300 K), the Re-doped WSe2 exhibits better adsorption of C2H4 over C2H2 and CO as the C2H4 has higher adsorption energy compared to the C2H2 and CO. Besides, V–I characteristics of the Re doped WSe2 layer after adsorption of the CO, C2H2, and C2H4 are detailed which signifies the efficacy of the Re doped WSe2 monolayer.
本文分析了掺杂铼(Re)的二硒化钨(WSe2)单层在检测一氧化碳(CO)、乙炔(C2H2)和乙烯(C2H4)等小气体分子方面的传感性能。密度泛函理论和非平衡态格林函数被用来研究经过重新装饰的 WSe2 单层在变压器油中溶解气体分析气体作用下的电气和几何结构。因此,带状图和状态密度等电化学特性得到了详细说明。研究还考察了吸附系统的回收能力、Mulliken 群体和吸附能量,以确定其稳定性。研究还表明,再掺杂 WSe2 单层会产生形变,从而使带隙变窄。在环境温度(273 K-300 K)下,再掺杂 WSe2 对 C2H4 的吸附效果优于 C2H2 和 CO,因为 C2H4 的吸附能高于 C2H2 和 CO。此外,掺 Re 的 WSe2 层在吸附 CO、C2H2 和 C2H4 后的 V-I 特性也很详细,这表明了掺 Re 的 WSe2 单层的功效。
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引用次数: 0
A coupled crystal inelasticity-phase field model for crack growth in polycrystalline nitinol microstructures 多晶镍钛诺微结构裂纹生长的晶体非弹性-相场耦合模型
IF 1.8 4区 材料科学 Q3 MATERIALS SCIENCE, MULTIDISCIPLINARY Pub Date : 2024-08-27 DOI: 10.1088/1361-651x/ad6fbf
Thirupathi Maloth, Pheobe Appel, Jonah Erlebacher, Somnath Ghosh
This paper introduces a comprehensive computational framework, comprising a finite deformation crystal inelasticity constitutive model and phase field model, for modeling crack growth in superelastic nitinol polycrystalline microstructures. The crystal inelasticity model represents crystal stretching and lattice rotation from elastic mechanisms, as well as local inelastic deformation due to austenite-martensite phase transformation. The phase field formulation decomposes the Helmholtz free energy density into stored elastic energy, phase transformation energy, and crack surface energy components. The elastic energy accounts for tension-compression asymmetry with the formation of the crack through a spectral decomposition. Kinetic Monte Carlo simulations generate equilibrium area fractions of different surface orientations, which serve as weights for the surface energy. An adaptive wavelet-enhanced hierarchical finite element (FE) model is introduced to alleviate high computational overhead in phase field crack simulations. Simulations with the coupled inelasticity phase field model are conducted under various loading conditions including Mode-I tension, a quasi-static Kalthoff experiment, and cyclic loading of polycrystalline microstructures. Crack propagation is effectively predicted by this model, providing valuable insights into the material mechanical behavior with growing cracks.
本文介绍了一种综合计算框架,包括有限变形晶体非弹性结构模型和相场模型,用于模拟超弹性镍钛诺多晶微结构中的裂纹生长。晶体非弹性模型表示了弹性机制引起的晶体拉伸和晶格旋转,以及奥氏体-马氏体相变引起的局部非弹性变形。相场公式将亥姆霍兹自由能密度分解为储存的弹性能、相变能和裂纹表面能。弹性能通过频谱分解反映了裂纹形成时拉伸与压缩的不对称。动力学蒙特卡洛模拟产生了不同表面取向的平衡面积分数,作为表面能的权重。引入了自适应小波增强分层有限元(FE)模型,以减轻相场裂纹模拟的高计算开销。利用耦合非弹性相场模型在各种加载条件下进行了模拟,包括模式 I 拉伸、准静态 Kalthoff 实验以及多晶微结构的循环加载。该模型有效地预测了裂纹的扩展,为了解材料在裂纹扩展时的机械行为提供了宝贵的见解。
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引用次数: 0
First-principles study of the interaction of solutes with ∑3(11-1) symmetric tilt grain boundaries in α-Fe α-Fe中溶质与∑3(11-1)对称倾斜晶界相互作用的第一性原理研究
IF 1.8 4区 材料科学 Q3 MATERIALS SCIENCE, MULTIDISCIPLINARY Pub Date : 2024-08-27 DOI: 10.1088/1361-651x/ad6ea9
R M Meftakhutdinov
The structural, cohesive and magnetic properties of a symmetric Σ3(70.53)[011](11-1) tilt grain boundary in pure bcc iron and with commonly used alloying elements (Si, Co, Mn, Ti, Cu, Mo, Nb, V, Cr and Ni) by means of density functional theory calculations are studied. Solubility and segregation energies were calculated for different positions of dissolved atoms. Calculations show a tendency for impurities to segregate near the boundary. It was found that the substituting Co, Cu and Ni in the layer adjacent to the boundary have an embrittling effect, while other atoms enhance the cohesion of the grains. Magnetic moments on GB atoms are significantly higher than those on bulk atoms.
通过密度泛函理论计算,研究了纯 bcc 铁和含有常用合金元素(Si、Co、Mn、Ti、Cu、Mo、Nb、V、Cr 和 Ni)的对称 Σ3(70.53)[011](11-1)倾斜晶界的结构、内聚力和磁性。计算了溶解原子不同位置的溶解度和偏析能。计算结果表明,杂质倾向于在边界附近发生偏析。研究发现,边界邻近层中的 Co、Cu 和 Ni 具有脆化作用,而其他原子则增强了晶粒的内聚力。GB 原子上的磁矩明显高于体原子上的磁矩。
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引用次数: 0
Interface stabilization and propagation in phase field models of solidification: resolving the issue of large driving forces 凝固相场模型中的界面稳定和传播:解决大驱动力问题
IF 1.8 4区 材料科学 Q3 MATERIALS SCIENCE, MULTIDISCIPLINARY Pub Date : 2024-08-13 DOI: 10.1088/1361-651x/ad691d
Murali Uddagiri, Marvin Tegeler, Ingo Steinbach
One of the long-standing problems in the phase field, namely, combining the principles of thermodynamics and capillarity with the numerical aspects of interface propagation in simulations, is re-investigated. Numerical schemes are discussed which allow for stable simulations with arbitrary driving forces, considering or excluding capillarity. We re-investigate a classical stabilization scheme that decouples interface stabilization from curvature evaluation, ensuring stable simulations even under large driving forces. A novel mathematical analysis gives a rigorous estimate for the time stepping and a numerical value of the required stabilization strength. The proposed stabilization scheme is benchmarked for three-dimensional dendritic growth under directional solidification conditions for different solidification speeds.
重新研究了相场中的一个长期存在的问题,即在模拟中将热力学和毛细管原理与界面传播的数值方面结合起来。讨论的数值方案允许在考虑或排除毛细作用的情况下,对任意驱动力进行稳定模拟。我们重新研究了一种经典的稳定方案,该方案将界面稳定与曲率评估分离开来,确保即使在较大的驱动力下也能进行稳定的模拟。新颖的数学分析给出了对时间步长的严格估计和所需稳定强度的数值。针对不同凝固速度下定向凝固条件下的三维树枝状生长,对所提出的稳定方案进行了基准测试。
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引用次数: 0
Effect of UEVC parameters on cutting surface quality and subsurface damage of single crystal γ-TiAl alloy via atomic simulation 通过原子模拟研究 UEVC 参数对单晶 γ-TiAl 合金切削表面质量和次表面损伤的影响
IF 1.8 4区 材料科学 Q3 MATERIALS SCIENCE, MULTIDISCIPLINARY Pub Date : 2024-08-11 DOI: 10.1088/1361-651x/ad6a74
Yuncui Chen, Baocheng Zhou, Huibin Zhu, Haiyan Li, Ruicheng Feng, Hui Cao and Chunli Lei
TiAl alloys are favored by the aerospace industry due to its excellent mechanical properties. However, its intrinsic brittleness, the use of conventional cutting (CC) process leads to the problems of high cutting force and high cutting temperature, which in turn affects the machined surface quality. Ultrasonic elliptical vibratory cutting (UEVC) has been proved to be an effective method to improve the surface quality and reduce the subsurface damage of difficult-to-machine materials. This paper compares the effects of CC and UEVC processes on cutting forces and subsurface damage based on molecular dynamics simulation methods, and the effects of elliptical vibration frequencies and amplitude ratios (AR) on surface morphology, roughness, and subsurface damage are investigated. The results show that the cutting force and subsurface damage in the UEVC process are reduced compared with that in the CC. Due to the vibration frequency, the subsurface damage is mainly dominated by atomic clusters, and both surface and subsurface masses show an optimization trend as the vibration frequency decreases. In terms of the AR, the surface quality is better at an AR of 2/3, with less activation of immovable dislocations, and the degree of subsurface damage decreases as the AR increases, and a relatively stable defective structure emerges when the AR is 1/2. The simulation results facilitate an atomic-scale comprehension of the removal mechanism of UEVC and further provide a theoretical foundation for the surface mass and subsurface damage mechanism and optimization of vibrational parameters of UEVC single crystal γ-TiAl alloy.
钛铝合金因其优异的机械性能而受到航空航天工业的青睐。然而,由于其本身的脆性,使用传统切削(CC)工艺会导致切削力大、切削温度高的问题,进而影响加工表面质量。超声波椭圆振动切割(UEVC)已被证明是改善难加工材料表面质量和减少表面下损伤的有效方法。本文基于分子动力学模拟方法,比较了 CC 和 UEVC 工艺对切削力和表面下损伤的影响,并研究了椭圆振动频率和振幅比 (AR) 对表面形态、粗糙度和表面下损伤的影响。结果表明,与 CC 工艺相比,UEVC 工艺的切削力和表面下损伤都有所降低。由于振动频率的原因,次表层损伤主要以原子团为主,随着振动频率的降低,表面和次表层质量都呈现出优化趋势。就 AR 而言,当 AR 为 2/3 时,表面质量较好,不可移动位错的活化程度较低;随着 AR 的增大,次表层损伤程度减小;当 AR 为 1/2 时,出现了相对稳定的缺陷结构。模拟结果有助于在原子尺度上理解 UEVC 的去除机制,并进一步为 UEVC 单晶 γ-TiAl 合金的表面质量和次表面损伤机制以及振动参数的优化提供了理论基础。
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引用次数: 0
Crack configuration influence on fracture behavior and stress shielding: insights from molecular dynamics simulations 裂纹构造对断裂行为和应力屏蔽的影响:分子动力学模拟的启示
IF 1.8 4区 材料科学 Q3 MATERIALS SCIENCE, MULTIDISCIPLINARY Pub Date : 2024-08-11 DOI: 10.1088/1361-651x/ad691b
O C Şen and R Janisch
The fracture behavior of the Ti–Al alloy is significantly affected by its nano-lamellar structure. However, further investigation is still required to fully comprehend how the initial crack configuration influences the lamellar Ti–Al’s deformation behavior. Although molecular dynamics simulations are a great way to study crack-tip interactions in interface-dominated microstructures, the design of the simulation can have an impact on the behavior that is predicted. To shed light on this matter and at the same time to understand the impact of the specific interface structure, a systematic study of crack-tip interface interactions in nano-lamellar two-phase Ti–Al was carried out. The type of interface and crack configuration were varied in these simulations to distinguish between the effects of the microstructure and the crack geometry. Results show that the semi-coherent pseudo twin ( PT) interface is the strongest barrier for crack propagation while the coherent true twin interface ( TT) is the weakest. After a thorough review of the contributing factors, it is evident that the orientation of the crack has a greater impact on its propagation than the aspect ratio of the crack. The stress shielding effectiveness of lamellar interfaces is strongly dependent on the crack configuration. However, regardless of the initial crack set-up, the coherent TT interface appears to be the most effective interface in terms of shielding.
钛铝合金的断裂行为受到其纳米层状结构的显著影响。然而,要完全理解初始裂纹构造如何影响片状 Ti-Al 的变形行为,仍需进一步研究。虽然分子动力学模拟是研究界面主导型微结构中裂纹尖端相互作用的重要方法,但模拟的设计会对预测的行为产生影响。为了阐明这一问题,同时了解特定界面结构的影响,我们对纳米板层双相钛铝中的裂纹尖端界面相互作用进行了系统研究。在这些模拟中,界面的类型和裂纹的构造各不相同,以区分微观结构和裂纹几何形状的影响。结果表明,半相干伪孪晶(PT)界面是裂纹扩展的最强障碍,而相干真孪晶(TT)界面则是最弱的障碍。在对各种因素进行深入研究后,我们发现裂纹的走向比裂纹的长宽比对裂纹扩展的影响更大。片状界面的应力屏蔽效果在很大程度上取决于裂纹的构造。然而,无论最初的裂纹设置如何,就屏蔽效果而言,相干 TT 接口似乎是最有效的接口。
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引用次数: 0
Effect of Bi content and temperature on the shear mechanical properties of Fe-Bi nanocomposites: a molecular dynamics study 铋含量和温度对铁铋纳米复合材料剪切机械性能的影响:分子动力学研究
IF 1.8 4区 材料科学 Q3 MATERIALS SCIENCE, MULTIDISCIPLINARY Pub Date : 2024-08-07 DOI: 10.1088/1361-651x/ad691c
Pan Li, Fazhan Wang, Guangyuan Li, Yuan Fan, Zhanwen Chen, Menghui Liu and Hong Wu
In this study, the effects of Bi content and temperature on the mechanical properties of Fe–Bi nanocomposites were investigated using molecular dynamics simulation. The research reveals that the nanocomposite’s shear strength reaches a peak of 3.785 GPa at a Bi content of 0.15%, attributed to the impediment of dislocation movement by twin boundaries during shearing, resulting in a dynamic ‘Hall–Petch’ effect and exceptional shear performance of the material. The abundant twinning induced around Bi phase inclusions introduces orientational disparities within the crystal, leading to grain misalignments, with dislocations in the grains slipping near the twin boundaries. In the nanocomposites, <100> dislocations merely act as initial sites for reactions, reducing their impact on the material’s strength and fracture behavior. The maximum stress decreases with increasing temperature while the magnitude of atomic transformations increases. The proportion of atoms at grain boundaries is higher at higher temperatures, and the arrangement of atoms at grain boundaries is more complex. At a temperature of 100 K, the dislocation density is highest with the smallest variation, forming a reinforced region within the material. The above results have significant implications for the design of environmentally friendly Bi-containing free-cutting steels.
本研究利用分子动力学模拟研究了 Bi 含量和温度对 Fe-Bi 纳米复合材料力学性能的影响。研究发现,当 Bi 含量为 0.15% 时,纳米复合材料的剪切强度达到 3.785 GPa 的峰值,这是由于孪晶边界在剪切过程中阻碍了位错运动,从而产生了动态 "霍尔-佩奇 "效应,使材料具有优异的剪切性能。Bi 相夹杂物周围产生的大量孪晶在晶体内部引入了取向差异,导致晶粒错位,晶粒中的位错在孪晶边界附近滑动。在纳米复合材料中,位错只是作为反应的初始位置,减少了对材料强度和断裂行为的影响。最大应力随着温度的升高而减小,而原子转变的幅度却在增大。温度越高,晶界处的原子比例越高,晶界处的原子排列也越复杂。温度为 100 K 时,位错密度最高,变化最小,在材料内部形成一个强化区域。上述结果对设计环保型含铋易切削钢具有重要意义。
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引用次数: 0
Crystal structure identification with 3D convolutional neural networks with application to high-pressure phase transitions in SiO2 利用三维卷积神经网络识别晶体结构,并将其应用于二氧化硅的高压相变
IF 1.8 4区 材料科学 Q3 MATERIALS SCIENCE, MULTIDISCIPLINARY Pub Date : 2024-08-04 DOI: 10.1088/1361-651x/ad64f3
Linus C Erhard, Daniel Utt, Arne J Klomp and Karsten Albe
Efficient, reliable and easy-to-use structure recognition of atomic environments is essential for the analysis of atomic scale computer simulations. In this work, we train two neuronal network (NN) architectures, namely PointNet and dynamic graph convolutional NN (DG-CNN) using different hyperparameters and training regimes to assess their performance in structure identification tasks of atomistic structure data. We show benchmarks on simple crystal structures, where we can compare against established methods. The approach is subsequently extended to structurally more complex SiO2 phases. By making use of this structure recognition tool, we are able to achieve a deeper understanding of the crystallization process in amorphous SiO2 under shock compression. Lastly, we show how the NN based structure identification workflows can be integrated into OVITO using its python interface.
高效、可靠且易于使用的原子环境结构识别对于原子尺度计算机模拟分析至关重要。在这项工作中,我们使用不同的超参数和训练机制训练两种神经元网络(NN)架构,即 PointNet 和动态图卷积 NN(DG-CNN),以评估它们在原子结构数据的结构识别任务中的性能。我们展示了简单晶体结构的基准测试,并与已有方法进行了比较。随后,我们将该方法扩展到结构更为复杂的 SiO2 相。利用这种结构识别工具,我们能够更深入地了解冲击压缩下非晶态二氧化硅的结晶过程。最后,我们展示了如何利用 Python 界面将基于 NN 的结构识别工作流程集成到 OVITO 中。
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引用次数: 0
First principles validation of energy barriers in Ni75Al25 Ni75Al25 中能量障碍的第一原理验证
IF 1.8 4区 材料科学 Q3 MATERIALS SCIENCE, MULTIDISCIPLINARY Pub Date : 2024-07-23 DOI: 10.1088/1361-651x/ad5c85
Adam Fisher, Julie B Staunton, Huan Wu and Peter Brommer
Precipitates in nickel-based superalloys form during heat treatment on a time scale inaccessible to direct molecular dynamics simulation, but can be studied using kinetic Monte Carlo (KMC) modelling. This requires reliable values for the barrier energies separating distinct configurations over the trajectory of the system. In this study, we validate vacancy migration barriers found with the Activation-Relaxation Technique nouveau (ARTn) method in partially ordered Ni75Al25 with a monovacancy using published potentials for the atomic interactions against first-principles methods. In a first step, we confirm that the ARTn barrier energies agree with those determined with the nudged elastic band (NEB) method. As the number of atoms used in those calculations is too great for direct ab initio calculations, we cut the cell size to 255 atoms, thus controlling finite size effects. We then use the plane-wave density functional theory code CASTEP and its inbuilt NEB method in the smaller cells. This provides us with a continuous validation chain from first principles to KMC simulations with interatomic potentials (IPs). We evaluate the barrier energies of five further IPs with NEB, demonstrating that none yields values with sufficient reliability for KMC simulations, with some of them failing completely. This is a first step towards quantifying the errors incurred in KMC simulations of precipitate formation and evolution.
镍基超合金中的沉淀物在热处理过程中形成,其时间尺度无法直接进行分子动力学模拟,但可以使用动力学蒙特卡罗(KMC)建模进行研究。这就需要在系统轨迹上分隔不同构型的势垒能的可靠值。在本研究中,我们利用已公布的原子相互作用势能与第一原理方法,验证了在部分有序的单共价物 Ni75Al25 中通过新活化-松弛技术(ARTn)方法发现的空位迁移势垒。首先,我们确认 ARTn 势垒能与用裸弹带(NEB)方法确定的势垒能一致。由于在这些计算中使用的原子数量过多,无法进行直接的 ab initio 计算,因此我们将单元尺寸缩小到 255 个原子,从而控制了有限尺寸效应。然后,我们在较小的单元中使用平面波密度泛函理论代码 CASTEP 及其内置 NEB 方法。这为我们提供了从第一原理到使用原子间势(IP)进行 KMC 模拟的连续验证链。我们用 NEB 评估了另外五个 IP 的势垒能,结果表明,没有一个 IP 能产生足够可靠的 KMC 模拟值,其中一些 IP 完全失效。这是量化 KMC 模拟沉淀形成和演化所产生误差的第一步。
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引用次数: 0
Temperature effects on the sheath-core bar interface of compositeinsulators: a molecular dynamics and DFT study 复合绝缘体鞘芯棒界面的温度效应:分子动力学和 DFT 研究
IF 1.9 4区 材料科学 Q3 MATERIALS SCIENCE, MULTIDISCIPLINARY Pub Date : 2024-07-18 DOI: 10.1088/1361-651x/ad64f2
Jun Xie, Longyin Qiao, Ziqian Liu, Xiaoyu Shi, Ping Huang
The functioning condition of composite insulators is greatly influenced by the sheath-mandrel interface. In this work, the effects of temperature on the sheath-mandrel system are examined using molecular modeling, taking into account both density functional theory (DFT) and molecular dynamics (MD). The system's interfacial free volume, HOMO/LUMO, number of hydrogen bonds, bond order, center-of-mass distance, and other characteristics define its degradation mechanism. The findings demonstrate that elevated temperatures have the potential to increase the interfacial free volume, the center-of-mass distance, and significantly reduce the number of hydrogen bonds. In addition, DFT simulations show that the bonding strength and non-bonding forces between the interfaces weaken with increasing temperature.High temperatures significantly boost the reactivity of the epoxy resin and silicone rubber chains, indicating that the system's response with some intruders will be catalyzed by the temperature increase.This work looks at the temperature dependence of the sheath-core bar interface degradation from a microscopic perspective, which is important for enhancing the overall performance of composite insulators.
复合绝缘体的工作状态在很大程度上受到鞘-棒界面的影响。在这项研究中,我们通过分子建模,同时考虑密度泛函理论(DFT)和分子动力学(MD),研究了温度对鞘-棒体系的影响。该体系的界面自由体积、HOMO/LUMO、氢键数量、键序、质量中心距和其他特征决定了其降解机制。研究结果表明,温度升高有可能增加界面自由体积和质量中心距离,并显著减少氢键数量。此外,DFT 模拟显示,界面间的键合强度和非键合力随着温度的升高而减弱。高温显著提高了环氧树脂和硅橡胶链的反应活性,表明系统对某些入侵者的反应将受到温度升高的催化。这项工作从微观角度研究了护套-芯棒界面降解的温度依赖性,这对提高复合绝缘体的整体性能非常重要。
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引用次数: 0
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Modelling and Simulation in Materials Science and Engineering
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