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High‐entropy materials (HEMs), which are newly manufactured compounds that contain five or more metal cations, can be a platform with desired properties, including improved electrocatalytic performance owing to the inherent complexity. Here, a strain engineering methodology is proposed to design transition‐metal‐based HEM by Li manipulation (LiTM) with tunable lattice strain, thus tailoring the electronic structure and boosting electrocatalytic performance. As confirmed by the experiments and calculation results, tensile strain in the LiTM after Li manipulation can optimize the d‐band center and increase the electrical conductivity. Accordingly, the as‐prepared LiTM‐25 demonstrates optimized oxygen evolution reaction and hydrogen evolution reaction activity in alkaline saline water, requiring ultralow overpotentials of 265 and 42 mV at 10 mA cm−2, respectively. More strikingly, LiTM‐25 retains 94.6% activity after 80 h of a durability test when assembled as an anion‐exchange membrane water electrolyzer. Finally, in order to show the general efficacy of strain engineering, we incorporate Li into electrocatalysts with higher entropies as well. Strain engineering of high‐entropy materials has been carried out with the involvement of Li. The presence of lattice strain leads to an upward shift of the transition‐metal d‐band centers, optimizing the free energy of the absorbate while increasing the electronic conductivity, which in turn greatly improves the electrocatalytic performance. As‐prepared high‐entropy electrocatalysts show excellent water‐splitting stability in alkaline saline water. Highlights An innovative design and fabrication method for high‐entropy electrocatalysts with strain strategies is reported. Optimized electrocatalysts show ultralow oxygen evolution reaction (265 mV) and hydrogen evolution reaction (42 mV) overpotentials at 10 mV cm−2 in alkaline saline water. The universal enhanced catalytic activity of high‐entropy electrocatalysts is verified by the addition of metal species. It is proved that the presence of lattice strain optimizes the d‐band center of the active site.

High entropy oxides (HEOs), based on the incorporation of multiple‐principal cations into the crystal lattice, offer the possibility to explore previously inaccessible oxide compositions and unconventional properties. Here it is demonstrated that despite the chemical complexity of HEOs external stimuli, such as epitaxial strain, can selectively stabilize certain magneto‐electronic states. Epitaxial (Co 0.2 Cr 0.2 Fe 0.2 Mn 0.2 Ni 0.2 ) 3 O 4 ‐HEO thin films are grown in three different strain states: tensile, compressive, and relaxed. A unique coexistence of rocksalt and spinel‐HEO phases, which are fully coherent with no detectable chemical segregation, is revealed by transmission electron microscopy. This dual‐phase coexistence appears as a universal phenomenon in (Co 0.2 Cr 0.2 Fe 0.2 Mn 0.2 Ni 0.2 ) 3 O 4 epitaxial films. Prominent changes in the magnetic anisotropy and domain structure highlight the strain‐induced bidirectional control of magnetic properties in HEOs. When the films are relaxed, their magnetization behavior is isotropic, similar to that of bulk materials. However, under tensile strain, the hardness of the out‐of‐plane (OOP) axis increases significantly. On the other hand, compressive straining results in an easy OOP magnetization and a maze‐like magnetic domain structure, indicating the perpendicular magnetic anisotropy. Generally, this study emphasizes the adaptability of the high entropy design strategy, which, when combined with coherent strain engineering, opens additional prospects for fine‐tuning properties in oxides.

We propose a straightforward and effective approach to design, by pattern-tunable strain-engineering, photonic topological insulators supporting high quality factors edge states. Chiral strain-engineering creates opposite synthetic gauge fields in two domains resulting in Landau levels with the same energy spacing but different topological numbers. The boundary of the two topological domains hosts robust time-reversal and spin-momentum-locked edge states, exhibiting high quality factors due to continuous strain modulation. By shaping the synthetic gauge field, we obtain remarkable field confinement and tunability, with the strain strongly affecting the degree of localization of the edge states. Notably, the two-domain design stabilizes the strain-induced topological edge state. The large potential bandwidth of the strain-engineering and the opportunity to induce the mechanical stress at the fabrication stage enables large scalability for many potential applications in photonics, such as tunable microcavities, new lasers, and information processing devices, including the quantum regime.

Controlling, and in many cases minimizing, friction is a goal that has long been pursued in history. From the classic Amontons–Coulomb law to the recent nanoscale experiments, the steady-state friction is found to be an inherent property of a sliding interface, which typically cannot be altered on demand. In this work, we show that the friction on a graphene sheet can be tuned reversibly by simple mechanical straining. In particular, by applying a tensile strain (up to 0.60%), we are able to achieve a superlubric state (coefficient of friction nearly 0.001) on a suspended graphene. Our atomistic simulations together with atomically resolved friction images reveal that the in-plane strain effectively modulates the flexibility of graphene. Consequently, the local pinning capability of the contact interface is changed, resulting in the unusual strain-dependent frictional behavior. This work demonstrates that the deformability of atomic-scale structures can provide an additional channel of regulating the friction of contact interfaces involving configurationally flexible materials.

Using epitaxy and the misfit strain imposed by an underlying substrate, it is possible to elastically strain oxide thin films to percent levels—far beyond where they would crack in bulk. Under such strains, the properties of oxides can be dramatically altered. In this article, we review the use of elastic strain to enhance ferroics, materials containing domains that can be moved through the application of an electric field (ferroelectric), a magnetic field (ferromagnetic), or stress (ferroelastic). We describe examples of transmuting oxides that are neither ferroelectric nor ferromagnetic in their unstrained state into ferroelectrics, ferromagnets, or materials that are both at the same time (multiferroics). Elastic strain can also be used to enhance the properties of known ferroic oxides or to create new tunable microwave dielectrics with performance that rivals that of existing materials. Results show that for thin films of ferroic oxides, elastic strain is a viable alternative to the traditional method of chemical substitution to lower the energy of a desired ground state relative to that of competing ground states to create materials with superior properties.

The deformation of interatomic distances with respect to those of the perfect crystal generates atomic-level strain. In nanoalloys, strain can arise because of finite size, morphology, domain structure and lattice mismatch between their atomic compounds. Strain can strongly affect the functional properties of nanoalloys, as it alters their electronic energy levels. Moreover, atomic-level strain generates atomic-level stress, which in turn results in distortions induced by strain. When the stress accumulated in a nanoalloy exceeds a certain level, the particle can relax that stress by undergoing structural transitions such as shape and/or chemical ordering transitions. Atomic-level strain is then a powerful tool to control and manipulate the structural and functional properties of nanoalloys. This requires a combined theoretical and experimental approach both to deeply understand the physical origin of strain, and to characterize it with a sub-angstrom resolution. Here, we present a theoretical analysis of the main sources of strain in nanoalloys, we analyse how atomic-level strain can be experimentally measured with transmission electron microscopy, we discuss its effect on the functional properties of nanoalloys, finally we describe how atomic-level stress arises from atomic-level strain, and how stress can induce structural transformations at the nanoscale.

Elastic strain engineering offers a new route to enable high-performance catalysts, electrochemical energy conversion devices, separation membranes and memristors. By applying mechanical stress, the inherent energy landscape of reactions involved in the material can be altered. This is the so-called mechano-chemical coupling. Here we discuss how elastic strain activates reactions on metals and oxides. We also present analogies to strained polymer reactions. A rich set of investigations have been performed on strained metal surfaces over the last 15 years, and the mechanistic reasons behind strain-induced reactivity are explained by an electronic structure model. On the other hand, the potential of strain engineering of oxides for catalytic and energy applications has been largely underexplored. In oxides, mechanical stress couples to reaction and diffusion kinetics by altering the oxygen defect formation enthalpy, migration energy barrier, adsorption energy, dissociation barrier, and charge transfer barrier. A generalization of the principles for stress activated reactions from polymers to metals to oxides is offered, and the prospect of using elastic strain to tune reaction and diffusion kinetics in functional oxides is discussed.

Transition metals serve as pivotal electrocatalysts dueto tunable electronic structures and adsorption properties. Strain modulation emerges as a powerful strategy to tailor their electronic configurations (e.g., d‐band center, surface energy) and adsorption behaviors, thereby optimizing reaction kinetics, product selectivity, and durability in different electrochemical processes. This review summarizes structural and theoretical advances in strain engineering for key electrochemical reactions, including hydrogen evolution, oxygen reduction, and CO2 reduction. In particular, different crystal facets exhibit distinct electrocatalytic performances, which are closely associated with facet‐dependent strain, as strain modulations vary significantly across different facets. These facet‐dependent strain effects highlight the critical role of surface structure, while density functional theory calculations and experimental techniques (e.g., epitaxial growth, mechanical deformation) provide mechanistic insights. Current challenges in nanoscale strain control and future opportunities for efficient electrocatalyst design toward sustainable energy are also outlined. This review offers significant insights into strain engineering, opening more opportunities for developing catalysts that enhance sustainable energyapplications. This review systematically consolidates the structural and theoretical advances of strain engineering in key electrochemical reactions, establishing a comprehensive framework that connects strain‐induced modifications in electronic structures and surface properties to catalytic performance optimization. This review will supply critical insights into strain effects, bridging theoretical advancements and experimental breakthroughs to guide rational catalyst design.

Recently, strain engineering has been shown to be a powerful and flexible means of tailoring the properties of ABO 3 perovskite thin films. The effect of epitaxial strain on the structure of the perovskite unit cell can induce a host of interesting effects, these arising from either polar cation shifts or rotation of the oxygen octahedra, or both. In the multi-ferroic perovskite bismuth ferrite (BiFeO 3 –BFO), both degrees of freedom exist, and thus a complex behaviour may be expected as one plays with epitaxial strain. In this paper, we review our results on the role of strain on the ferroic transition temperatures and ferroic order parameters. We find that, while the Néel temperature is almost unchanged by strain, the ferroelectric Curie temperature strongly decreases as strain increases in both the tensile and compressive ranges. Also unexpected is the very weak influence of strain on the ferroelectric polarization value. Using effective Hamiltonian calculations, we show that these peculiar behaviours arise from the competition between antiferrodistortive and polar instabilities. Finally, we present results on the magnetic order: while the cycloidal spin modulation present in the bulk survives in weakly strained films, it is destroyed at large strain and replaced by pseudo-collinear antiferromagnetic ordering. We discuss the origin of this effect and give perspectives for devices based on strain-engineered BiFeO 3 .

Experimental discovery of ultralarge elastic deformation in nanoscale diamond and machine learning of its electronic and phonon structures have created opportunities to address new scientific questions. Can diamond, with an ultrawide bandgap of 5.6 eV, be completely metallized, solely under mechanical strain without phonon instability, so that its electronic bandgap fully vanishes? Through first-principles calculations, finite-element simulations validated by experiments, and neural network learning, we show here that metallization/demetallization as well as indirect-to-direct bandgap transitions can be achieved reversibly in diamond below threshold strain levels for phonon instability. We identify the pathway to metallization within six-dimensional strain space for different sample geometries. We also explore phonon-instability conditions that promote phase transition to graphite. These findings offer opportunities for tailoring properties of diamond via strain engineering for electronic, photonic, and quantum applications.