Metropolis Monte Carlo simulations of the eutectic NaK alloy are performed using the Second Moment Approximation (SMA) model potential across a wide range of temperatures at constant pressure. The alloy structure and thermodynamics are analyzed along with the atomic level structures using a variety of structure identification methods. Both enthalpy and density are followed along an annealing process that reveals a clear melting point around 250 K. At lower temperatures, two thermodynamic branches are identified as crystalline and amorphous solids.
在~1.2 GPa压力下，在Fe 40 Ni 40 P 14 B6合金的过冷液体区，对两块体非晶合金圆片进行了短时间热压凝固。当凝固温度Ts较低时，两块体非晶Fe 40 Ni 40 P 14 B6合金盘不能实现连接。只有当Ts达到675 K附近时，两个非晶Fe 40 Ni 40 P14 B6合金盘才具有足够低的粘度以在短时间内完全熔合在一起，并且所得压块保留约90%的非晶相。为了进一步提高凝固温度Ts，大量的晶化将发生并导致金属玻璃的脆化。
Investigation on Vibrational, Optical and Structural Properties of an Amorphous Se$_{0.80}$S$_{0.20}$ Alloy Produced by Mechanical Alloying
用Raman光谱、X射线衍射、扩展X射线吸收精细结构（EXAFS）和光学吸收光谱研究了机械合金化法制备的非晶态Se $_{0.80}$ S $_{0.20}$合金，并对其总结构因子和EXAFS数据进行了反向蒙特卡罗模拟。它的振动模式，光学间隙和平均原子间距离和平均配位数的结构特性进行了测定和比较，发现为非晶硒$_{0.90}$ S $_{0.10}$合金。结果表明，配位数，原子间距离和间隙能量依赖于硫浓度。
EXAFS, XRD and RMC studies of an Amorphous Ga$_{50}$Se$_{50}$ Alloy Produced by Mechanical Alloying
利用扩展X射线吸收精细结构（EXAFS）和X射线衍射（XRD）技术，以及反向蒙特卡罗（RMC）方法对机械合金化（MA）制备的非晶Ga $_{50}$ Se $_{50}$合金的局域原子有序性进行了研究。通过EXAFS分析和RMC模拟确定了第一邻体的配位数和原子间距离。RMC模拟还提供了部分对分布函数$G^{\text{RMC}}_{\text{Ga-Ga}}(r)$、$G^{\text{RMC}}_{\text{Ga-Se}}(r)$和$G^{\text{RMC}}_{\text{Se-Se}}(r)$。结果表明，MA法制备的非晶态Ga $_{50}$ Se $_{50}$合金的局域结构与相应晶体的局域结构有很大的不同，这是因为在金属玻璃的第一配位壳层中存在Ga $_{50}$ Se $_{50}$晶体中所不允许的Se-Se对。
Magnetic properties of amorphous Co$_x$Nb$_{100-x}$ alloys produced by mechanical alloying
从元素粉末开始通过机械合金化制备三种非晶Co $_x$ Nb $_{100-x}$合金，Co $_{25}$ Nb $_{75}$、Co $_{57}$ Nb $_{43}$和Co $_{80}$ Nb $_{20}$。用交变梯度磁力仪（AGFM）测定了它们的磁性能，并由磁滞回线得到了它们的剩磁、饱和磁场和矫顽磁场。合金具有相对高的饱和磁场，其随着成分变得富含Co而降低。矫顽力和回复磁化强度在57%at.Co附近达到最佳值，使得{ \em a}-Co $_{57}$ Nb $_{43}$成为三种合金中最硬的磁性材料。进一步添加Co产生软合金。
Hidden orders in amorphous structures: extraction of nearest neighbor networks of amorphous Nd-Fe alloys with Gabriel graph analyses
采用有限温度第一性原理分子动力学熔体淬火模拟方法，采用Delaunay和Gabriel图方法，对计算生成的Nd-Fe合金在不同成分比下的非晶结构进行了分析，通过比较由Delaunay和Gabriel图得到的径向分布函数和整个系统的径向分布函数，结果表明，在所研究的非晶系统中，Gabriel图很好地代表了第一近邻网络。通过Gabriel图分析，我们对非晶态Nd-Fe合金的配位结构进行了统计分析。我们发现，配位数的分布范围取决于组成比。分析了相邻三个原子间的角分布，发现富Nd和富Fe样品中的角分布表现不同。我们发现，随着Nd含量的增加，非晶系统中的有序性增强，这对应于高Nd含量时晶界相的出现[T. T. Sasaki等人，材料学报。115，269-277（2016）]。
Investigation on Anharmonicity, Vibrational Anisotropy and Thermal Expansion of an Amorphous Ni$_{46}$Ti$_{54}$ Alloy Produced by Mechanical Alloying using Extended X-ray Absorption Fine Structure
提出了一种利用基于累积膨胀的扩展X射线吸收精细结构（EXAFS）分析得到的平行和垂直于原子间键的相关均方相对位移（MSRD）研究非谐性、振动各向异性和热膨胀的方法，并将其应用于机械合金化制备的非晶态Ni $_{46}$ Ti $_{54}$合金。通过在不同温度下对Ni和Ti K边的EXAFS测量，获得了$\text{MSRD}_\parallel$、$\text{MSRD}_\perp$和实分布函数$\varrho_{ij}(r,T)$的累积量$C_1^*$、$C_2^*$和$C_3^*$的热行为，以及与平行和垂直运动有关的爱因斯坦温度和频率，提供了关于原子间势的非谐性的信息。振动各向异性以及垂直运动对总无序和热膨胀的贡献。
First principles molecular dynamics study of amorphous Si\sub{1-x}Ge\sub{x}:H alloys
利用第一性原理局域基分子动力学模拟研究了非晶Si \sub{1-x} Ge \sub{x}：H合金的结构、动力学和电子学性质。分析了非晶网络的拓扑结构和缺陷。结构变化和缺陷数量的增加已被发现作为Ge原子百分比从x=0.1增加到x=0.5。随着Ge浓度的增加，电子态密度呈现出带隙减小、带隙中缺陷态和带尾缺陷态增加的趋势。态密度带尾的研究显示出指数（Urbach）行为。的迁移率间隙估计作为Ge浓度的函数。
Since the pioneering efforts of Duwez and coworkers in 1965, when a solid amorphous phase of Pd-Si ($a$-PdSi) was obtained in the vicinity of the eutectic concentration, much work has been done. However, some points related to the atomic structures remain to be systematized. In this work, 8 amorphous Pd$_{100-c}$Si$_{c}$ alloys (c = 2.5, 5, 10, 13.34, 15, 17.5, 20, and 22 at %) were generated by molecular dynamics $ab$ $initio$ simulations; the short-range structure is analyzed using several correlation functions, like Pair Distribution Functions, reduced Pair Distribution Functions, Plane Ang…
Molecular dynamics simulations are performed to provide a detailed understanding of the functional degradation of shape memory alloys at small scale. The origin of the experimentally reported accumulation of plastic deformation and the anomalous sudden increase of the residual strain under cyclic mechanical loading are explained by detailed insights into the relevant atomic scale processes. Our work reveals that the mechanical response of shape-memory-alloy pillars under cyclic compression is significantly influenced by the presence of an amorphous-like surface region as experimentally induced…
Modeling the amorphous structure of a mechanically alloyed Ti50Ni25Cu25 alloy using anomalous wide-angle x-ray scattering and reverse Monte Carlo simulations
通过19 h的机械合金化制备了Ti 50 Ni 25 Cu 25非晶合金。异常广角X射线散射数据收集在六个能量和六个总散射因子。通过考虑Ni和Cu K边附近两个能量下的数据，得到了Ni和Cu原子周围的两个微分反常散射因子，表明这两个原子周围的化学环境是不同的。这8个因子被用作反向蒙特卡罗方法的输入数据，用于计算部分结构因子STi-Ti（K）、STi-Cu（K）、STi-Ni（K）、SCu-Cu（K）、SCu-Ni（K）和SNi-Ni（K）。通过傅立叶变换，得到了部分对分布函数GTi-Ti（r），GTi-Cu（r），GTi-Ni（r），GCu-Cu（r），GCu-Ni（r）和GNi-Ni（r），并确定了第一邻体的配位数和原子间距。
Amorphous complexions have recently been demonstrated to simultaneously enhance the ductility and stability of certain nanocrystalline alloys. In this study, three quinary alloys (Cu-Zr-Hf-Mo-Nb, Cu-Zr-Hf-Nb-Ti, and Cu-Zr-Hf-Mo-W) are studied to test the hypothesis that increasing the chemical complexity of the grain boundaries will result in thicker amorphous complexions and further stabilize a nanocrystalline microstructure. Significant boundary segregation of Zr, Nb, and Ti is observed in the Cu-Zr-Hf-Nb-Ti alloy, which creates a quaternary interfacial composition that limits average grain …
The porous titanium nickelide is very popular in various industries due to unique combination of physical and mechanical properties such as shape memory effect, high corrosion resistance, and biocompatibility. The non-equilibrium molecular dynamics simulation was applied to study the influence of porosity degree on mechanical properties of porous amorphous titanium nickelide at uniaxial tension, uniaxial compression, and uniform shear. We have found that the porous amorphous alloy is characterized by a relatively large value of Young's modulus in comparison to its crystalline analogue. It has …
Soft magnetic materials have low coercive fields and high permeability. Recently, nanocrystalline alloys obtained using annealing amorphous alloys have attracted much interest since nanocrystalline alloys with small grain sizes of tens of nanometers exhibit low coercive fields comparable to that of amorphous alloys. Since nanocrystalline soft magnetic materials attain remarkable soft magnetic properties by controlling the grain size, the crystal grains' microstructure has a substantial influence on the soft magnetic properties. In this research, we examined the magnetic properties of Fe-Si-B-P…
Grain boundary-based mechanisms are known to control the plastic deformation and failure of nanocrystalline metals, with manipulation of the boundary structure a promising path for tuning this response. In this study, the role of interfacial structural disorder on plasticity and failure of nanocrystalline Cu-Zr alloys is investigated with in situ scanning electron microscopy tensile deformation experiments. Two model materials are created, one with only the typical ordered grain boundaries and another with amorphous intergranular films interspersed into the boundary network, while the microstr…
Theoretical predictions of the ideal strength of materials range from E/30 to E/10 (E is Young's modulus). However, despite intense interest over the last decade, the value of the ideal strength that can be attained experimentally for metals remains a mystery (1-5). In this study, we demonstrated the unprecedented strength of an amorphous Cu-Zr alloy that surpassed the E/10 limit. Laser-induced shock experiments were conducted on Cu50Zr50 to explore its strength and failure mechanisms at ultrahigh strain rates. The material demonstrated a high spall strength of 9.8 GPa, approximately 1/13 of i…
A computational alloy design framework for the promotion of amorphous grain boundary complexions
Hopkins Extreme Materials Institute, Johns Hopkins University（约翰斯·霍普金斯大学极端材料研究所）；Department of Materials Science and Engineering, Johns Hopkins University（约翰斯·霍普金斯大学材料科学与工程系）；Department of Materials Science and Engineering, University of California Los Angeles（加州大学洛杉矶分校材料科学与工程系）；Department of Mechanical and Aerospace Engineering, University of California Los Angeles（加州大学洛杉矶分校机械与航空航天工程系）；Department of Materials Science and Chemical Engineering, Stony Brook University（石溪大学材料科学与化学工程系）；Institute for Advanced Computational Science, Stony Brook University（石溪大学高级计算科学研究所）；Materials Science and Technology Division, Oak Ridge National Laboratory（橡树岭国家实验室材料科学与技术部）
Thin film metallic glasses undergoing devitrification can form partially crystallized or fully crystallized materials with novel structural and magnetic properties. The development of desired and tunable properties of such systems drives the need to understand the mechanism of their thermal evolution at the atomic level. Co-sputtered amorphous Ni-Zr alloy thin films which were thermally annealed in steps of 200 deg C from room temperature up to 800 deg C, were observed to undergo an amorphous-to-crystalline transformation. Evolutions in local atomic structure, including oxide formation and dep…
Two new refractory amorphous high-entropy alloys (RAHEAs) within the W--Ta--Cr--V and W--Ta--Cr--V--Hf systems were herein synthesized using magnetron-sputtering and tested under high-temperature annealing and displacing irradiation using \textit{in situ} Transmission Electron Microscopy. While the WTaCrV RAHEA was found to be unstable under such tests, additions of Hf in this system composing a new quinary WTaCrVHf RAHEA was found to be a route to achieve stability both under annealing and irradiation. A new effect of nanoprecipitate reassembling observed to take place within the WTaCrVHf RAH…
Microscopy and diffraction measurements are presented of ultrathin binary alloy films of ruthenium and molybdenum that are obtained by standard sputter deposition. For compositions close to Ru50Mo50, we find the films to be amorphous. The amorphicity of the films is accompanied by a significant reduction of the roughness with respect to the roughness of equally thick films of either ruthenium or molybdenum. We ascribe this to the absence of the grain structure that is characteristic of the polycrystalline films of the separate elements.
