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1. Pressure–temperature route from disordered BCC to a 2 × 2 × 2 B2 superstructure

   https://doi.org/10.1038/s41598-025-33729-6  

   Sereika, Raimundas; Pope, Andrew D; Knight, Caleb M; Chakrabarty, Kallol; Vohra, Yogesh K (December 2025, Scientific Reports)

   The interplay between configurational entropy and the enthalpy of ordered structures governs phase stability in compositionally complex alloys. In the refractory alloy Re0.6(NbTiZrHf)0.4, this balance is particularly delicate: pressure stabilizes a disordered body-centred-cubic (bcc) solid solution over the ambient hexagonal Laves phase via a martensitic route. Using in situ laser heating with synchrotron X-ray diffraction in a diamond-anvil cell, we demonstrate that the metastable bcc phase can be controllably transformed into a large-scale 2×2×2 B2-type superstructure with primitive-cubic symmetry (Pm3 ̅m). This long-period ordered phase is crystallographically distinct from conventional B2 ordering in multicomponent alloys, establishing a pathway to achieve chemical ordering from pressure-stabilized solid solutions. More broadly, these findings demonstrate that combining compression with subsequent thermal activation can unlock recoverable three-dimensional superstructures, offering new opportunities to tailor strength, transport properties, and stability in compositionally complex alloys. 

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2. Communication: From close-packed to topologically close-packed: Formation of Laves phases in moderately polydisperse hard-sphere mixtures

   https://doi.org/10.1063/1.5028279  

   Lindquist, Beth A.; Jadrich, Ryan B.; Truskett, Thomas M. (May 2018, The Journal of Chemical Physics)

   Particle size polydispersity can help to inhibit crystallization of the hard-sphere fluid into close-packed structures at high packing fractions and thus is often employed to create model glass-forming systems. Nonetheless, it is known that hard-sphere mixtures with modest polydispersity still have ordered ground states. Here, we demonstrate by computer simulation that hard-sphere mixtures with increased polydispersity fractionate on the basis of particle size and a bimodal subpopulation favors the formation of topologically close-packed C14 and C15 Laves phases in coexistence with a disordered phase. The generality of this result is supported by simulations of hard-sphere mixtures with particle-size distributions of four different forms. 

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3. Effect of surface steps on chemical ordering in the subsurface of Cu(Au) solid solutions

   https://doi.org/https://doi.org/10.1103/PhysRevB.103.035401  

   K. Liu, S. Zhang (December 2020, Physical review)

   Atomic steps are typically assumed to only influence surface phenomena of solids. In contrast, here we show, using in situ atomic-resolution electron microscopy observations and atomistic modeling, the pronounced effect from surface steps in inducing compositional and structural evolution in the subsurface of a Cu(Au) solid solution. We find that Au surface segregation results in a stacked sequence of Cu-Au ordered phases in the subsurface. The presence of a monatomic step at the surface induces the formation of an anti-phase boundary that extends from the surface step to deeper layers by maintaining the same composition profile associated with each terrace. The bunching of surface steps induces chemical disordering of the Cu-Au ordered phases in the subsurface region of the bunched steps. These results demonstrate the instant propagation of surface dynamics of atomic steps into the subsurface region and can find broader applicability in utilizing surface defects to tune the composition and structure in the subsurface of alloys. 

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4. Role of Al additions in secondary phase formation in CoCrFeNi high entropy alloys

   https://doi.org/10.1063/5.0117280  

   Anber, Elaf A.; Smith, Nathan C.; Liaw, Peter K.; Wolverton, Christopher M.; Taheri, Mitra L. (October 2022, APL Materials)

   Al x CoCrFeNi High Entropy Alloys (HEAs), also referred to as multiprincipal element alloys, have attracted significant interest due to their promising mechanical and structural properties. Despite these attributes, Al x CoCrFeNi HEAs are susceptible to phase separation, forming a wide range of secondary phases upon aging, including NiAl–B2 and Cr-rich phases. Controlling the formation of these phases will enable the design of age-hardenable alloys with optimized corrosion resistance. In this study, we examine the critical role of Al additions and their concentration on the stability of the CoCrFeNi base alloy, uncovering the connections between Al composition and the resulting microstructure. Addition of 0.1 mol fraction of Al destabilizes the single-phase microstructure and results in the formation of Cr-rich body-centered-cubic (bcc) phases. Increasing the composition of Al (0.3–0.5 mol fraction) results in the formation of more complex coprecipitates, NiAl–B2 and Cr-rich bcc. Interestingly, we find that the increase of the Al content stimulates the formation of NiAl–B2 phases, increases the overall density of secondary phases, and influences the content of Cr in Cr-rich bcc phases. Density functional theory calculations of simple decomposition reactions of Al x CoCrFeNi HEAs corroborate the tendency for precipitate formation of these phases upon increased Al composition. Additionally, these calculations support previous results, indicating the base CoCrFeNi alloy to be unstable at low temperature. This work provides a foundation for predictive understanding of phase evolution, opening the window toward designing innovative alloys for targeted applications. 

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5. First-Order Phase Transition in Liquid Ag to the Heterogenous G-Phase

   https://doi.org/10.1021  

   Qi, An; Johnson, William L.; Samwar, Konrad; Corona, Sydney L.; Goddard III, William A. (January 2020, The journal of physical chemistry letters)

   A molten metal is an atomic liquid that lacks directional bonding and is free from chemical ordering effects. Experimentally, liquid metals can be undercooled by up to ∼20% of their melting temperature but crystallize rapidly in subnanosecond time scales at deeper undercooling. To address this limited metastability with respect to crystallization, we employed molecular dynamics simulations to study the thermodynamics and kinetics of the glass transition and crystallization in deeply undercooled liquid Ag. We present direct evidence that undercooled liquid Ag undergoes a first-order configurational freezing transition from the high-temperature homogeneous disordered liquid phase (L) to a metastable, heterogeneous, configura-tionally ordered state that displays elastic rigidity with a persistent and finite shear modulus, μ. We designate this ordered state as the G-phase and conclude it is a metastable non-crystalline phase. We show that the L−G transition occurs by nucleation of the G-phase from the L-phase. Both te L- and G-phases are metastable because both ultimately crystallize. The observed first-order transition is reversible: the G-phase displays a first-order melting transition to the L-phase at a coexistence temperature, TG,M. We develop a thermodynamic description of the two phases and their coexistence boundary. 

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