Acta Materialia最新文献

{"title":"Geometrically Morphological Theory in predictions of dendritic shapes with six-fold crystalline symmetry","authors":"Liubov V. Toropova, Peter K. Galenko, Dmitri V. Alexandrov","doi":"10.1016/j.actamat.2025.121232","DOIUrl":"https://doi.org/10.1016/j.actamat.2025.121232","url":null,"abstract":"Motivated by important applications in materials physics, we study the shape of dendritic crystals with six-fold crystalline symmetry grown in aqueous solutions of various substances and pure water. Based on recently developed Geometrically Morphological Theory [Philos. Trans. R. Soc. A 378 (2020) 20190243; Phys. Lett. A 501 (2024) 129375] we demonstrate that the shape of the main stem and internal/external envelope in the secondary branches of dendrite at the steady-state growth mode is described by the scaling law <span><span style=\"\"></span><span data-mathml='<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow is=\"true\"><mi is=\"true\">z</mi><mrow is=\"true\"><mo is=\"true\">(</mo><mi is=\"true\">x</mi><mo is=\"true\">)</mo></mrow><mo linebreak=\"goodbreak\" linebreakstyle=\"after\" is=\"true\">∝</mo><mo linebreak=\"goodbreak\" linebreakstyle=\"after\" is=\"true\">−</mo><mo is=\"true\">|</mo><mi is=\"true\">x</mi><msup is=\"true\"><mrow is=\"true\"><mo is=\"true\">|</mo></mrow><mrow is=\"true\"><mi is=\"true\">n</mi></mrow></msup></mrow></math>' role=\"presentation\" style=\"font-size: 90%; display: inline-block; position: relative;\" tabindex=\"0\"><svg aria-hidden=\"true\" focusable=\"false\" height=\"2.779ex\" role=\"img\" style=\"vertical-align: -0.812ex;\" viewbox=\"0 -846.5 5753.3 1196.3\" width=\"13.363ex\" xmlns:xlink=\"http://www.w3.org/1999/xlink\"><g fill=\"currentColor\" stroke=\"currentColor\" stroke-width=\"0\" transform=\"matrix(1 0 0 -1 0 0)\"><g is=\"true\"><g is=\"true\"><use xlink:href=\"#MJMATHI-7A\"></use></g><g is=\"true\" transform=\"translate(635,0)\"><g is=\"true\"><use xlink:href=\"#MJMAIN-28\"></use></g><g is=\"true\" transform=\"translate(389,0)\"><use xlink:href=\"#MJMATHI-78\"></use></g><g is=\"true\" transform=\"translate(962,0)\"><use xlink:href=\"#MJMAIN-29\"></use></g></g><g is=\"true\" transform=\"translate(2264,0)\"><use xlink:href=\"#MJMAIN-221D\"></use></g><g is=\"true\" transform=\"translate(3320,0)\"><use xlink:href=\"#MJMAIN-2212\"></use></g><use is=\"true\" x=\"4099\" xlink:href=\"#MJMAIN-7C\" y=\"-1\"></use><g is=\"true\" transform=\"translate(4377,0)\"><use xlink:href=\"#MJMATHI-78\"></use></g><g is=\"true\" transform=\"translate(4950,0)\"><g is=\"true\"><use is=\"true\" xlink:href=\"#MJMAIN-7C\"></use></g><g is=\"true\" transform=\"translate(278,477)\"><g is=\"true\"><use transform=\"scale(0.707)\" xlink:href=\"#MJMATHI-6E\"></use></g></g></g></g></g></svg><span role=\"presentation\"><math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow is=\"true\"><mi is=\"true\">z</mi><mrow is=\"true\"><mo is=\"true\">(</mo><mi is=\"true\">x</mi><mo is=\"true\">)</mo></mrow><mo is=\"true\" linebreak=\"goodbreak\" linebreakstyle=\"after\">∝</mo><mo is=\"true\" linebreak=\"goodbreak\" linebreakstyle=\"after\">−</mo><mo is=\"true\">|</mo><mi is=\"true\">x</mi><msup is=\"true\"><mrow is=\"true\"><mo is=\"true\">|</mo></mrow><mrow is=\"true\"><mi is=\"true\">n</mi></mrow></msup><","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"641 1","pages":""},"PeriodicalIF":9.4,"publicationDate":"2025-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144341416","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Unusual synchronous behavior of polarization and relaxation in aurivilius superlattice","authors":"S. Liu, T. Ochirkhuyag, W. Feng, B. He, L. Wu, H. Qi, J. Chen, W. Wang, H. Zheng, Y. Liu, D. Odkhuu","doi":"10.1016/j.actamat.2025.121184","DOIUrl":"https://doi.org/10.1016/j.actamat.2025.121184","url":null,"abstract":"Bismuth layer-structure ferroelectric (BLSF) materials have potential for energy storage applications because of their high-temperature stability and excellent resistance to electric breakdown; however, they suffer from an asynchronous behavior of polarization and relaxation upon an impurity element. Herein, using systematic computational and experimental investigations, we report that, in sharp contrast to typical perovskite and bismuth layer-structure ferroelectric structures, the high-content La in Bi<span><math><msub is=\"true\"><mrow is=\"true\"></mrow><mrow is=\"true\"><mn is=\"true\">3</mn></mrow></msub></math></span>TiNbO<span><math><msub is=\"true\"><mrow is=\"true\"></mrow><mrow is=\"true\"><mn is=\"true\">9</mn></mrow></msub></math></span> can produce greatly enhanced dielectric relaxation and out-of-plane polarization simultaneously. The underlying mechanism is the manipulation of La-O bonds within sequence-disordered Bi<span><math><msub is=\"true\"><mrow is=\"true\"></mrow><mrow is=\"true\"><mn is=\"true\">2</mn></mrow></msub></math></span>O<span><math><msub is=\"true\"><mrow is=\"true\"></mrow><mrow is=\"true\"><mn is=\"true\">2</mn></mrow></msub></math></span> layered counterpart rather than the quasiperovskite counterpart in the <span><math><mrow is=\"true\"><mi is=\"true\">F</mi><mi is=\"true\">m</mi><mi is=\"true\">m</mi><mi is=\"true\">m</mi></mrow></math></span> phase dominant superlattice, which is essentially contrariwise in the <span><math><mrow is=\"true\"><mi is=\"true\">A</mi><msub is=\"true\"><mrow is=\"true\"><mn is=\"true\">2</mn></mrow><mrow is=\"true\"><mn is=\"true\">1</mn></mrow></msub><mi is=\"true\">a</mi><mi is=\"true\">m</mi></mrow></math></span> phase dominant sample prepared in most previous experiments. Furthermore, we demonstrate that atomic defect engineering, specifically line dislocation resulting from the replacement of Bi with La<span><math><msup is=\"true\"><mrow is=\"true\"></mrow><mrow is=\"true\"><mn is=\"true\">3</mn><mo is=\"true\">+</mo></mrow></msup></math></span> ions in Bi<span><math><msub is=\"true\"><mrow is=\"true\"></mrow><mrow is=\"true\"><mn is=\"true\">3</mn></mrow></msub></math></span>TiNbO<span><math><msub is=\"true\"><mrow is=\"true\"></mrow><mrow is=\"true\"><mn is=\"true\">9</mn></mrow></msub></math></span>, can provide an additional out-of-plane polarization. As a result, a high recoverable energy density <span><math><msub is=\"true\"><mrow is=\"true\"><mi is=\"true\">W</mi></mrow><mrow is=\"true\"><mi is=\"true\" mathvariant=\"normal\">rec</mi></mrow></msub></math></span> of 8.7 J/cm<span><math><msup is=\"true\"><mrow is=\"true\"></mrow><mrow is=\"true\"><mn is=\"true\">3</mn></mrow></msup></math></span> and efficiency <span><math><mi is=\"true\">η</mi></math></span> of 80.5%, together with excellent thermal stability and an ultra-fast discharge rate, are achieved in Bi<span><math><msub is=\"true\"><mrow is=\"true\"></mrow><mrow is=\"true\"><mn is=\"true\">2</mn></mrow></msub></math></span>LaTiNbO<span><math><msub is=\"true\"><mrow is=\"true\"></mrow><mrow is=\"true\"><mn is=\"true\">9</mn></mrow></","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"16 1","pages":""},"PeriodicalIF":9.4,"publicationDate":"2025-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144341428","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Tunable Lamb Wave Bandgap Based on 90° Diffuse Domain Walls in Ferroelectric Thin Films","authors":"Sizheng Zheng, Xu Hou, Peng Han, Tao Xu, Takahiro Shimada, Jie Wang","doi":"10.1016/j.actamat.2025.121284","DOIUrl":"https://doi.org/10.1016/j.actamat.2025.121284","url":null,"abstract":"Ferroelectric and piezoelectric thin films hold significant potential for tunable acoustic devices. While the elastodynamic properties of ferroelectric thin films have been studied for various domain structures, the influence of diffuse domain walls on acoustic waves remains unexplored. In this study, using a phase-field perturbation model, the effect of 90° diffuse domain walls on Lamb wave propagation in ferroelectric thin films is investigated. Modal analysis reveals that the local negative shear modulus induces localized shear vibrations within the diffuse domain walls, disrupting the symmetry of Lamb wave mode in ferroelectric thin films. This disruption further leads to strong coupling between distorted symmetric and antisymmetric Lamb modes, resulting in multiple bandgap formations. The bandgaps can be successfully tuned through changing the spacing of domain walls, which can be easily realized by applying external strains or electric fields. In addition, the nonlinear scaling laws are predicted for the bandgaps, which are in good agreement with previous experimental reports. This work suggests an effective method for designing tunable acoustic metamaterials based on ferroelectric thin films.","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"14 1","pages":""},"PeriodicalIF":9.4,"publicationDate":"2025-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144337645","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dislocation density measurements on Mg alloys reveal surprising temperature dependences","authors":"Michael Ritzo, Jishnu Bhattacharyya, Péter Nagy, Gergely Farkas, Jenő Gubicza, Kristián Máthis, Sean Agnew","doi":"10.1016/j.actamat.2025.121273","DOIUrl":"https://doi.org/10.1016/j.actamat.2025.121273","url":null,"abstract":"There has been tremendous worldwide effort to determine the deformation mechanisms responsible for the behavior of Mg and other non-cubic metal alloys. Here, <em>ex-situ</em> X-ray line profile analysis (XLPA) and electron backscattered diffraction (EBSD) are employed to examine the densities of dislocations with &lt;a&gt;, &lt;c&gt; and &lt;c+a&gt; Burgers vectors within Mg alloy sheet materials tested in uniaxial tension at various temperatures. EBSD reveals geometrically necessary dislocation (GND) accumulation near grain boundaries during low-temperature plasticity, whereas GNDs are primarily associated with grain subdivision after high-temperature deformation. Similar to previous studies, the current XLPA results suggest that the relative density of &lt;a&gt; dislocations drops with increasing temperature more rapidly than &lt;c&gt; and &lt;c+a&gt;. This implies that non-basal slip is more prevalent at elevated temperatures. However, published <em>in-situ</em> XLPA and the present noise-filtered EBSD measurements of GNDs suggest only weak temperature dependence of the relative densities. The fraction of &lt;a&gt;-type GNDs actually <em>increases</em> slightly with temperature. It is hypothesized that &lt;a&gt; dislocations are more prone to recover, be incorporated into dislocation walls, than are &lt;c&gt; or &lt;c+a&gt; dislocations because such recovery would render &lt;a&gt; dislocations less “visible” to the XLPA approach. These experimental results provide support for a recently published polycrystal model (Ritzo <em>et</em> al. <em>Mater. Sci. Eng. A.</em> 839 (2022) 142581) which suggested that increased amounts of &lt;a&gt; dislocation climb could account for the observed changes in plastic anisotropy, texture evolution, rate sensitivity, and activation energy, which occur as the temperature approaches and exceeds half of the melting temperature.","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"15 1","pages":""},"PeriodicalIF":9.4,"publicationDate":"2025-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144335174","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Achieving efficient damping performance tuning in NiTi alloy via laser powder bed fusion","authors":"Shiyu Zhong, Jun Song, Ying Li, Lei Zhang, Shuo Wang, Xu Zheng, Bo Song, Dingfei Zhang, Jian Lu","doi":"10.1016/j.actamat.2025.121281","DOIUrl":"https://doi.org/10.1016/j.actamat.2025.121281","url":null,"abstract":"NiTi alloys exhibit an impressive damping effect at the damping peak temperature (<em>T_p</em>), and aligning <em>T_p</em> with target temperatures presents significant application value. Traditionally, tuning the damping performance of NiTi alloys demanded precise modifications to raw material composition and complex thermomechanical processing. This study achieves an efficient tuning of <em>T_p</em> across a broad 93 K range via laser powder bed fusion (LPBF), eliminating the need for material modifications and complex treatments. Comprehensive experiments and simulations are conducted to reveal the mechanism. Adjusting the laser scanning speed during LPBF modulates the laser–powder interaction, resulting in variations in temperature, lifespan, and volume of the molten pool. These variations facilitate the manipulation of Ni evaporation, enabling the regulation of Ni content and, thus, the tuning of <em>T_p</em>. Notably, a 0.1 at.% increase in Ni content results in a 7.55 K decrease in <em>T_p</em>. Despite the efficient tuning of <em>T_p</em>, the damping peak intensity remains high (0.06–0.11), indicating the preservation of the desired damping effect. Additionally, this study discusses the composition and influencing factors of damping peaks in LPBF NiTi alloys. Furthermore, high-damping, lightweight NiTi porous structures are fabricated by LPBF, highlighting the unique advantages over conventional routines. Overall, this study provides new insights and a framework for the efficient tuning of damping performance in NiTi alloys, paving the way for advanced applications of high-damping materials.","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"7 1","pages":""},"PeriodicalIF":9.4,"publicationDate":"2025-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144335173","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Electron migration pathways in S-scheme GaP-TiO2 photocatalysts and their implications for photocatalytic hydrogen production","authors":"Vendula Meinhardová, Lada Dubnová, Marcin Kobielusz, Daniel Kouba, Stanislav Slang, Pengwei Huo, Oleksandr Matvieiev, Wojciech Macyk, Kamila Kočí, Libor Čapek","doi":"10.1016/j.actamat.2025.121274","DOIUrl":"https://doi.org/10.1016/j.actamat.2025.121274","url":null,"abstract":"The integration of gallium phosphide (GaP) with TiO₂ provides a promising approach to enhance the separation of photogenerated electrons and holes, thus improving photocatalytic efficiency. GaP-TiO₂ photocatalysts (0.4-7.6 wt% GaP) were prepared via the wet impregnation of commercial GaP onto TiO₂ synthesized using sol-gel method in a reverse micellar environment. The surface element composition and structural, textural, optical, and electronic properties of the GaP-TiO₂ photocatalysts were investigated. The results confirm the successful formation of an S-scheme heterostructure in the GaP-TiO₂ composite and reveal the charge carrier migration pathway. This heterostructure, combined with a photocurrent doubling effect induced by methanol in the reaction, significantly enhances hydrogen production during the photocatalytic decomposition of aqueous methanol solutions. The improved performance of these photocatalysts is attributable to the synergistic interaction of GaP and TiO₂, facilitating separation and reducing recombination, thus boosting overall photocatalytic performance.","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"1 1","pages":""},"PeriodicalIF":9.4,"publicationDate":"2025-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144335176","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Novel mechanism of ultra-high adiabatic shear susceptibility in FCC-based high-entropy alloys via high-content nanoprecipitate dissolution","authors":"Yao Xiao, Qinglei Zeng, Kaihui Xun, Jun Ding, Linjing Wang, Liang Wang, Yaojian Liang, Ke Jin, Shengxin Zhu, Yang Ren, Gang Sha, Lu Wang, Haosen Chen, Yunfei Xue","doi":"10.1016/j.actamat.2025.121280","DOIUrl":"https://doi.org/10.1016/j.actamat.2025.121280","url":null,"abstract":"Adiabatic shear bands (ASBs) are a crucial failure mechanism of metals and alloys subjected to impact loading. The formation mechanism of ASBs in an FCC-based high-entropy alloy (HEA) featuring high-content coherent nanoprecipitates was investigated. Unlike traditional FCC-structured alloys, which generally exhibit low shear banding capabilities, the FCC-structured HEA presented herein displays ultrahigh adiabatic shear susceptibility (ASS) under dynamic loading. A novel mechanism induced by the instantaneous dissolution of high-content L1₂ nanoprecipitates at relatively low temperatures is proposed to be responsible for the enhanced shear instability. At room temperature, these high-content L1₂ nanoprecipitates significantly increase the strength; however, under dynamic loading, deformation concentration causes a local temperature rise, triggering the instantaneous dissolution of nanoprecipitates. This induces a dramatic reduction in the local shear strength and promotes ASB formation. The combined effects of the nanosized features, low-energy interfaces, and spinodal-like structures of the precipitates contribute to the instantaneous dissolution process at relatively low temperatures. This novel shearing-band mechanism suggests a novel approach for designing ductile alloys with enhanced ASS.","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"44 1","pages":""},"PeriodicalIF":9.4,"publicationDate":"2025-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144335300","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Compositional-structural inhomogeneity and multi-layered oxide film formation on high-entropy alloys","authors":"Huaqing Yi, Mengtian Liang, Jinpeng Zhang, Bingbing Yin, Jianyu Huang, Fugang Qi, Zhenhua Yang, Guangwen Zhou, Qianqian Jin, Jian Chen, Yi Yang","doi":"10.1016/j.actamat.2025.121278","DOIUrl":"https://doi.org/10.1016/j.actamat.2025.121278","url":null,"abstract":"The wide compositional range and diverse elemental combinations in high-entropy alloys give rise to complex oxide scales, posing significant challenges in understanding the mechanisms governing local compositional and structural evolution during oxidation. This work investigates the mechanisms underlying the formation of the multi-layered oxide scale on the AlCoFeNiTi high-entropy alloys. The results show that the thermodynamic predominance for the formation of protective Al₂O₃ and TiO₂, coupled with the insufficient conditions for the establishment of a continuous oxide film, results in the development of a mixed inner oxide layer. This mixed layer facilitates the outward diffusion of alloying elements. Incomplete filling of the cavities at the forefront of the inner oxide layer by oxide growth leads to partial backfilling of Ni, thereby creating a localized Ni-rich layer. The formation of multiple oxide layers is governed by the interplay of thermodynamic driving force, elemental diffusivities, and the homogeneity of oxygen distribution. Additionally, kinetically captured solute atoms can alter the formation energy of oxides, influencing the spatial arrangement of different phases within the scale. The enrichment of Ni and Fe—driven by extended structural defects in the oxide scale—further leads to the precipitation of NiO<em>_x</em> and FeO<em>_x</em> clusters within the TiO₂ lattice. These insights provide a broader understanding of multi-layer oxide formation in Ti-containing high-entropy alloys and other alloys incorporating 3d transition metals, contributing to the design of oxidation-resistant high-entropy materials.","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"46 1","pages":""},"PeriodicalIF":9.4,"publicationDate":"2025-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144335175","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Modeling disordered hyperuniform heterogeneous materials: Microstructure representation, field fluctuations and effective properties","authors":"Liyu Zhong ,&nbsp;Sheng Mao ,&nbsp;Yang Jiao","doi":"10.1016/j.actamat.2025.121218","DOIUrl":"10.1016/j.actamat.2025.121218","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Disordered hyperuniform (DHU) materials are an emerging class of exotic heterogeneous material systems characterized by a unique combination of disordered local structures and a hidden long-range order, which endow them with unusual physical properties, including large isotropic photonic band gaps, superior resistance to fracture, and nearly optimal electrical and thermal transport properties, to name but a few. Here, we consider material systems possessing continuously varying local material properties &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;K&lt;/mi&gt;&lt;mrow&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mi&gt;x&lt;/mi&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/mrow&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; (e.g., thermal or electrical conductivity), modeled via a random field. We devise quantitative microstructure representation of the material systems based on a class of analytical spectral density function &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mover&gt;&lt;mrow&gt;&lt;mi&gt;χ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;̃&lt;/mo&gt;&lt;/mrow&gt;&lt;/mover&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;K&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mrow&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mi&gt;k&lt;/mi&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/mrow&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; associated with &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;K&lt;/mi&gt;&lt;mrow&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mi&gt;x&lt;/mi&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/mrow&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, possessing a power-law small-&lt;span&gt;&lt;math&gt;&lt;mi&gt;k&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; scaling behavior &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mover&gt;&lt;mrow&gt;&lt;mi&gt;χ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;̃&lt;/mo&gt;&lt;/mrow&gt;&lt;/mover&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;K&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mrow&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mi&gt;k&lt;/mi&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/mrow&gt;&lt;mo&gt;∼&lt;/mo&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mi&gt;k&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;α&lt;/mi&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;. By controlling the exponent &lt;span&gt;&lt;math&gt;&lt;mi&gt;α&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; and using a highly efficient forward generative model, we obtain realizations of a wide spectrum of distinct material microstructures spanning from hyperuniform (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;α&lt;/mi&gt;&lt;mo&gt;&gt;&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;) to nonhyperuniform (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;α&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;) to antihyperuniform (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;α&lt;/mi&gt;&lt;mo&gt;&lt;&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;) systems. Moreover, we perform a comprehensive perturbation analysis to quantitatively connect the fluctuations of the local material property to the fluctuations of the resulting physical fields. In the weak-contrast limit, i.e., when the fluctuations of the property are much smaller than the average value, our first-order perturbation theory reveals that the physical fields associated with Class-I hyperuniform materials (characterized by &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;α&lt;/mi&gt;&lt;mo&gt;≥&lt;/mo&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;) are also hyperuniform, albeit with a lower hyperuniformity exponent (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;α&lt;/mi&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;). As one moves away from this weak-contrast limit, the fluctuations of the physical field develop a diverging spectral density at the origin, revealed by our higher-order analysis. We also establish an end-to-end mapping connecting the spectral density of the local material property to the overall effective conduc","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"296 ","pages":"Article 121218"},"PeriodicalIF":8.3,"publicationDate":"2025-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144335177","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Complete structural studies of long period stacking ordered (LPSO) phases in the Y-Ni-Mg system by 3D electron diffraction","authors":"Pavlo Solokha, Riccardo Freccero, Mauro Gemmi, Iryna Andrusenko, Paola Parlanti, Enrico Mugnaioli, Gwladys Steciuk, Lukas Palatinus, Serena De Negri","doi":"10.1016/j.actamat.2025.121279","DOIUrl":"https://doi.org/10.1016/j.actamat.2025.121279","url":null,"abstract":"The crystal structures of three Y-Ni-Mg LPSO phases were directly solved from diffraction data of X-rays ((Mg@Y₈Ni₆)Mg₁₈, <em>tI</em>66-Nd_8+xRu₆Mg_19-x) and electrons ((Mg@Y₈Ni₆)₁₆Mg₅₀₅ and (Mg@Y₈Ni₆)₃Mg₁₅₄)). The latter two are modulated structures described in 6D(<em>Fm</em>-3<em>m</em>(α00)000(0α0)000(00α)000, <strong>q1</strong> = 0.441(6) <strong>a*, q2</strong> = 0.441(6) <strong>b*</strong>, and <strong>q3</strong> = 0.441(6) <strong>c*</strong>) and 5D (<em>R-</em>3<em>c</em>(αα0)00(-2α,α0)00, <strong>q₁</strong> = 0.1457(7) <strong>a*</strong> <em>+</em> 0.1457(7) <strong>b*, q₂</strong> = -0.2915(7) <strong>a*</strong>+ 0.1457(7) <strong>b*</strong>) superspaces, respectively. The 3D electron diffraction was applied here for the first time to LPSO compounds, turning out to be the only method successfully overcoming the numerous problems hampering their complete structure solution.The structural analysis of these compounds resulted in a generalized description of Y-Ni-Mg LPSO phases in terms of Mg@Y₈Ni₆ clusters more or less densely distributed in a Mg matrix, justifying the proposed formulas. LPSO classification based on the layer stacking modes is proposed, leading to <em>fcc</em> (<em>c</em>-type) and hybrid <em>fcc/hcp</em> (<em>(h)_ncc</em>-type) subfamilies, the former being identified in this work and including (Mg@Y₈Ni₆)Mg₁₈ as well as (Mg@Y₈Ni₆)₁₆Mg₅₀₅.The inter-clusters coordination in form of distorted anticuboctahedra or cuboctahedra is a further fingerprint of membership in either family. Increasing the magnesium content, the Mg@Y₈Ni₆ units tend to form aggregates at characteristic inter-cluster distances, the distribution of which is at the origin of the structural modulation.","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"29 1","pages":""},"PeriodicalIF":9.4,"publicationDate":"2025-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144334952","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}