Magnetically driven short-range order can explain anomalous measurements in CrCoNi

Abstract

The presence, nature, and impact of chemical short-range order in the multi-principal element alloy CrCoNi are all topics of current interest and debate. First-principles calculations reveal that its origins are fundamentally magnetic, involving repulsion between like-spin Co–Cr and Cr–Cr pairs that is complemented by the formation of a magnetically aligned sublattice of second-nearest-neighbor Cr atoms. Ordering models following these principles are found to predict otherwise anomalous experimental measurements concerning both magnetization and atomic volumes across a range of compositions. In addition to demonstrating the impact of magnetic interactions and resulting chemical rearrangement, the possible explanation of experiments would imply that short-range order of this type is far more prevalent than previously realized.

Multihyperuniform Long-Range Order in Medium-Entropy Alloys

“…In this letter, using the ternary silicon-germanium-tin (SiGeSn) MEA as an example, we provide strong numerical evidence for a hidden multihyperuniform long-range order (MHLRO) in MEAs, in which the normalized infinite-wavelength composition fluctuations for all atomic species are completely suppressed as in a perfect crystalline state. This is achieved by numerically rendering multihyperuniform realizations of the alloy, which naturally leads to the emergence of short-range order (SRO) quantitatively consistent with recently reported observations and results in stable lower-energy states compared to alloys possessing random structure and SQS without any atomic SRO [5][6][7]. We note that multihyperuniform patterns have been discovered previously in other physical and biological systems, e.g., chicken eyes [13].…”

“…The preponderance of previous studies typically assumed MEAs and HEAs possess a random or special quasirandom structure (SQS) [4] consisting of atoms of different types distributed on the sites of a crystalline lattice. However, a number of recent studies, in particular those on the chromium-cobalt-nickel (CrCoNi) MEAs, have discovered significant short-range order, often manifested as suppressed clustering of atoms of the same type, which are shown to lead to energetically favorable states of the alloys [5][6][7]. It is interesting to note that a natural consequence of the existence of such short-range order is the suppression of composition (or density) fluctuations.…”

A predictive model of surface adsorption in dissolution on transition metals and alloys

“…Importantly, our scheme describes well the effect of the chemical disorder of HEAs on the adsorption energy, providing a simple way to tune the chemical disorder for the property enhancement. Moreover, the short-range order is normally employed to study the chemical disorder of HEAs despite its controversy, 74,75 while our scheme goes beyond this concept and can well characterize the chemical-disorder effect regardless of the short-range order or disorder of HEAs.…”

Effects of Cr/Ni ratio on physical properties of Cr-Mn-Fe-Co-Ni high-entropy alloys

“…(1) Finite temperature effects (2) Atomic relaxations (3) Magnetic effects (4) Chemical short-range ordering (SRO) [116][117][118][119] (5) Strong dislocation/solute interactions [111] or lattice frictions [88] that counteract the elastic repulsion of the partials All these explanations are plausible, but their experimental validation/refutation is extremely challenging. Here, we limit our comments to points (1-3) since they were investigated in the present study.…”