Local Structure and Short-Range Order in a NiCoCr Solid Solution Alloy

Zhang, F. X.; Zhao, Shijun; Jin, Ke; Xue, Haizhou; Velişa, Gihan; Bei, Hongbin; Huang, Rong; Ko, J. Y. Peter; Pagan, Darren C.; Neuefeind, J.; Weber, William J.; Zhang, Yongfeng

doi:10.1103/physrevlett.118.205501

Cited by 318 publications

(137 citation statements)

References 49 publications

(65 reference statements)

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“…By contrast, according to the Materials Project [71], stable binary intermetallic compounds in the CrCoNi HEA such as CrCo3, CrNi2, and Co3Ni exist with the formation energies of -0.006, -0.021, and -0.022 eV/atom, respectively, which may enhance the tendency of CSRO in the metallic CrCoNi HEA. It is now well accepted that CSRO significantly reduces the configurational entropy [72,73]. In this regard, the semiconducting SiGeSn HEA should have a higher configurational entropy than the metallic CrCoNi HEA.…”

Section: Resultsmentioning

confidence: 99%

Semiconducting SiGeSn high-entropy alloy: A density functional theory study

Wang

Liu

Huang

2019

Journal of Applied Physics

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High-entropy alloys (HEAs), which have been intensely studied due to their excellent mechanical properties, generally refer to alloys with multiple equimolar or nearly equimolar elements.According to this definition, Si-Ge-Sn alloys with equal or comparable concentrations of the three Group IV elements belong to the category of HEAs. As a result, the equimolar elements of Si-Ge-Sn alloys likely cause their atomic structures to exhibit the same core effects of metallic HEAs such as lattice distortion. Here we apply density functional theory (DFT) calculations to show that the SiGeSn HEA indeed exhibits a large local distortion effect. Unlike metallic HEAs, our Monte Carlo and DFT calculations show that the SiGeSn HEA exhibits no chemical short-range order due to the similar electronegativity of the constituent elements, thereby increasing the configurational entropy of the SiGeSn HEA. Hybrid density functional calculations show that the SiGeSn HEA remains semiconducting with a band gap of 0.38 eV, promising for economical and compatible mid-infrared optoelectronics applications. We then study the energetics of neutral single Si, Ge, and Sn vacancies and (expectedly) find wide distributions of vacancy formation energies, similar to those found in metallic HEAs. However, we also find anomalously small lower bounds (e.g., 0.04 eV for a Si vacancy) in the energy distributions, which arise from the bond reformation near the vacancy. Such small vacancy formation energies and their associated bond reformations retain the semiconducting behavior of the SiGeSn HEA, which may be a signature feature of a semiconducting HEA that differentiates from metallic HEAs.

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Section: Resultsmentioning

confidence: 99%

Semiconducting SiGeSn high-entropy alloy: A density functional theory study

Wang

Liu

Huang

2019

Journal of Applied Physics

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“…In the simplest description, the local chemical environments of HEAs can be considered as representing a random distribution of different atomic species over crystal lattice sites, i.e., the maximum configurational entropy state (1). However, as has been discussed in the literature (20)(21)(22)(23), this description is likely to be oversimplified, as HEAs may display significant local chemical order, i.e., ordering in the first few neighbor atomic shells to enhance the number of energetically…”

mentioning

confidence: 99%

Tunable stacking fault energies by tailoring local chemical order in CrCoNi medium-entropy alloys

Ding

Asta

et al. 2018

Proc. Natl. Acad. Sci. U.S.A.

549

243

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High-entropy alloys (HEAs) are an intriguing new class of metallic materials due to their unique mechanical behavior. Achieving a detailed understanding of structure-property relationships in these materials has been challenged by the compositional disorder that underlies their unique mechanical behavior. Accordingly, in this work, we employ first-principles calculations to investigate the nature of local chemical order and establish its relationship to the intrinsic and extrinsic stacking fault energy (SFE) in CrCoNi medium-entropy solid-solution alloys, whose combination of strength, ductility, and toughness properties approaches the best on record. We find that the average intrinsic and extrinsic SFE are both highly tunable, with values ranging from -43 to 30 mJ⋅m and from -28 to 66 mJ⋅m, respectively, as the degree of local chemical order increases. The state of local ordering also strongly correlates with the energy difference between the face-centered cubic () and hexagonal close-packed () phases, which affects the occurrence of transformation-induced plasticity. This theoretical study demonstrates that chemical short-range order is thermodynamically favored in HEAs and can be tuned to affect the mechanical behavior of these alloys. It thus addresses the pressing need to establish robust processing-structure-property relationships to guide the science-based design of new HEAs with targeted mechanical behavior.

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“…The presence of Ni in structural alloys is known to play an important role in mitigation of swelling under irradiation [47]. Nickel, along with iron and tungsten, is the subject of extensive radiation damage research [2,48,49] for energy applications.…”

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confidence: 99%

Core Electrons in the Electronic Stopping of Heavy Ions

2018

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Electronic stopping power in the keV/Å range is accurately calculated from first principles for high atomic-number projectiles and the effect of core states is carefully assessed. The energy loss to electrons in self-irradiated nickel is studied using real-time time-dependent density functional theory. Different core states are explicitly included in the simulations to understand their involvement in the dissipation mechanism. The core electrons of the projectile are found to open additional dissipation channels as the projectile velocity increases. Almost all of the energy loss is accounted for, even for high projectile velocities, when core electrons as deep as 2s^{2}2p^{6} are explicitly treated. In addition to their expected excitation at high velocities, a flapping dynamical response of the projectile core electrons is observed at intermediate velocities. The empirical reference data are well reproduced in the projectile velocity range of 1.0-12.0 a.u. (1.5-210 MeV).

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Local Structure and Short-Range Order in a NiCoCr Solid Solution Alloy

Cited by 318 publications

References 49 publications

Semiconducting SiGeSn high-entropy alloy: A density functional theory study

Semiconducting SiGeSn high-entropy alloy: A density functional theory study

Tunable stacking fault energies by tailoring local chemical order in CrCoNi medium-entropy alloys

Core Electrons in the Electronic Stopping of Heavy Ions

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