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Mechanically responsive crystals are promising for actuators and microrobotics; however, achieving large reversible deformation with high durability remains challenging. Herein, A single‐component azobenzene crystal is reported to exhibit an abrupt and reversible stretching of over 8% along its long axis, driven by a thermally induced single‐crystal‐to‐single‐crystal phase transition. Single‐crystal X‐ray diffraction revealed a significant change in molecular packing distance along the long axis accompanied by the reorientation of CH–π interactions, leading to large macroscopic stretching/shrinking. Furthermore, visible light (435 nm) induced rapid, localized, and reversible stretching of the crystal via the photothermal effect, enabling the remote control of microparticle motion. This study reveals a rare combination of large anisotropic deformation, reversibility, and light responsiveness in a single‐component organic crystal, offering a new molecular platform for advancing micro‐energy conversion and soft robotics. Crystals of azobenzene compounds exhibit abrupt and reversible stretching and shrinking in response to thermal and photo stimulation. The single‐crystal‐to‐single‐crystal phase transition between two polymorphs involving reorientation of CH–π hydrogen interactions are demonstrated. Furthermore, the abrupt photoinduced stretching of the crystals is used to trigger microparticle transportation.

To understand the anisotropy dependence of the damage evolution and material removal during the machining process of MgF2 single crystals, nanoscratch tests of MgF2 single crystals with different crystal planes and directions were systematically performed, and surface morphologies of the scratched grooves under different conditions were analyzed. The experimental results indicated that anisotropy considerably affected the damage evolution in the machining process of MgF2 single crystals. A stress field model induced by the scratch was developed by considering the anisotropy, which indicated that during the loading process, median cracks induced by the tensile stress initiated and propagated at the front of the indenter. Lateral cracks induced by tensile stress initiated and propagated on the subsurface during the unloading process. In addition, surface radial cracks induced by the tensile stress were easily generated during the unloading process. The stress change led to the deflection of the propagation direction of lateral cracks. Therefore, the lateral cracks propagated to the workpiece surface, resulting in brittle removal in the form of chunk chips. The plastic deformation parameter indicated that the more the slip systems were activated, the more easily the plastic deformation occurred. The cleavage fracture parameter indicated that the cracks propagated along the activated cleavage planes, and the brittle chunk removal was owing to the subsurface cleavage cracks propagating to the crystal surface. Under the same processing parameters, the scratch of the (001) crystal plane along the [100] crystal-orientation was found to be the most conducive to achieving plastic machining of MgF2 single crystals. The theoretical results agreed well with the experimental results, which will not only enhance the understanding of the anisotropy dependence of the damage evolution and removal process during the machining of MgF2 crystals, but also provide a theoretical foundation for achieving the high-efficiency and low-damage processing of anisotropic single crystals.

Soft porous organic crystals with stimuli‐responsive single‐crystal‐to‐single‐crystal (SCSC) transformations are important tools for unraveling their structural transformations at the molecular level, which is of crucial importance for the rapid development of stimuli‐responsive systems. Carefully balancing the crystallinity and flexibility of materials is the prerequisite to construct advanced organic crystals with SCSC, which remains challenging. Herein, a squaraine‐based soft porous organic crystal (SPOC‐SQ) with multiple gas‐induced SCSC transformations and temperature‐regulated gate‐opening adsorption of various C1‐C3 hydrocarbons is reported. SPOC‐SQ is featured with both crystallinity and flexibility, which enable pertaining the single crystallinity of the purely organic framework during accommodating gas molecules and directly unveiling gas‐framework interplays by SCXRD technique. Thanks to the excellent softness of SPOC‐SQ crystals, multiple metastable single crystals are obtained after gas removals, which demonstrates a molecular‐scale shape‐memory effect. Benefiting from the single crystallinity, the molecule‐level structural evolutions of the SPOC‐SQ crystal framework during gas departure are uncovered. With the unique temperature‐dependent gate‐opening structural transformations, SPOC‐SQ exhibits distinctly different absorption behaviors towards C3H6 and C3H8, and highly efficient and selective separation of C3H6/C3H8 (v/v, 50/50) is achieved at 273 K. Such advanced soft porous organic crystals are of both theoretical values and practical implications. By balancing the crystallinity and flexibility, multiple gases‐induced single‐crystal‐to‐single‐crystal (SCSC) transformations of a novel soft porous organic crystal (SPOC) are discovered for not only elucidation of gas‐framework interplays and molecular‐scale shape‐memory effect at molecular level but also highly selective separation of propylene/propane, demonstrating the crucial significance of stimuli‐responsive SCSC transformations in guiding development of stimuli‐responsive systems.

The recently discovered 12442-type iron-based superconductors (IBSs), ACa2Fe4As4F2 (A = K, Rb, Cs), are intrinsically self-hole doped stoichiometric compounds that exhibit superconductivity with Tc = 30-33.5 K. In this paper, single crystals of Ni doped RbCa2(Fe1−xNix)4As4F2 with 0 ⩽ x ⩽ 0.1 have been successfully grown for the first time using a RbAs flux method and characterized by energy dispersive x-ray spectroscopy (EDS), x-ray diffraction (XRD), electrical resistivity, magnetic susceptibility, and Hall effect measurements. EDS and XRD measurements suggest that the Ni dopants are successfully doped into the crystal lattice. Based on the electrical resistivity and magnetization data, we construct the Tc-x phase diagram. Furthermore, it is found that Ni dopants not only introduce extra electrons that modify the topology of Fermi surface, but also act as impurity scattering centers that contribute to the pair breaking effect, i.e., the superconducting transition temperature Tc is suppressed with a rate of ΔTc/Ni-1% = −2.7 K. Intriguingly, such suppression of Tc and those in other similar hole doped IBSs, such as Ba0.6K0.4Fe2As2, Ba0.5K0.5Fe2As2, and EuRbFe4As4 with multiple nodeless gaps, can be well scaled together. Combining with relevant experimental data reported so far, we speculate that the pairing symmetry in 12442 system is very likely to be nodeless s±-wave. Finally, doping evolution of the upper critical field and its anisotropy are investigated and discussed in detail. Upon Ni doping, the coherence length ξc(0) is gradually increased and becomes larger than the FeAs interbilayer distance when x > 0.07, indicating that the nature of superconductivity changes from quasi two-dimensional (2D) to three-dimensional (3D). The anisotropy of the upper critical field γH close to Tc shows a nonmonotonic dependence on doping, which first increases from 6.7 at the pristine sample to its maximum 8.1 at x = 0.03, and then decreases to 3.7 at x = 0.09.

Among various metal-organic frameworks (MOFs), the zeolitic imidazole framework (ZIF), constructed by the regular arrangement of 2-methylimidazole and metal ions, has garnered significant attention due to its distinctive crystals and pore structures. Variations in the sizes and shapes of ZIF crystals have been reported by changing the synthesis parameters, such as the molar ratios of organic ligands to metal ions, choice of solvents, and temperatures. Nonetheless, the giant ZIF-8 single crystals beyond the typical range have rarely been reported. Herein, we present the synthesis of millimeter-scale single crystal ZIF-8 using the solvothermal method in N,N-diethylformamide. The resulting 1-mm single crystal is carefully characterized through N adsorption-desorption isotherms, scanning electron microscopy, and other analytical techniques. Additionally, single-crystal X-ray diffraction is employed to comprehensively investigate the framework's mobility at various temperatures.

This study investigates the single‐crystal‐to‐single‐crystal (SCSC) transformations of a copper(II) complex, [Cu(L1)2(acac)2]·2CH3OH (1), with an octahedral coordination geometry. The complex is synthesized using L1 (6‐phenyl‐1,3,5‐triazine‐4,2‐diamine; C9H18N5) and copper acetylacetonate. In this structure, copper is coordinated to four oxygen atoms from two monoanionic acetylacetonate (acac) ligands and two nitrogen atoms from two neutral L1 ligands. The transformation of complex 1 into complex 2 is achieved by heating at 80 °C for 48 h, leading to the removal of methanol. This elimination facilitates the formation of direct hydrogen bonds between the NH2 groups and nitrogen atoms of adjacent triazine rings, establishing a network of intermolecular interactions. Structural analysis revealed a 0.2 Å elongation of the copper–nitrogen bond in the L1 ligand as a result of methanol removal. Complementary characterization techniques, including FTIR, UV–vis spectroscopy, and Hirshfeld surface analysis, are employed to further elucidate the transformations. The impact of methanol elimination on the crystal structure is assessed, highlighting the changes in intermolecular interactions. A methanol‐ligated copper(II) complex undergoes a single‐crystal‐to‐single‐crystal transformation upon solvent loss, retaining crystallinity while reorganizing its coordination geometry and hydrogen‐bonding network.

Organic single crystals with long‐range molecular periodic ordering ensure superior charge‐transport properties and low defect density, which have been considered promising candidates for charge‐transporting materials in organic light‐emitting devices (OLEDs). The functional interfaces of OLEDs play a critical role in charge‐transporting and light‐emitting behaviors, while the interfacial properties of organic single crystals in OLEDs and their impact on device performance have been rarely investigated. Herein, two typical organic single crystals, 1,4‐bis(4‐Methylstyryl)benzene (BSB‐Me) and 2,6‐diphenylanthracene (DPA) with different molecular formulas and packing structures, are introduced as the single‐crystal hole‐transporting layers (HTLs) for a systematic investigation of the interfacial properties between single‐crystal HTLs and active emissive layers. BSB‐Me single‐crystal HTLs offer satisfied surface wettability and enhanced interfacial interaction, which dominate the charge‐transporting and light‐emitting behaviors of the OLEDs. Such improved interfacial properties are responsible for the superior light out‐coupling efficiency of BSB‐Me single‐crystal OLEDs with efficient exciton recombination and minimal Joule heat loss. In consequence, BSB‐Me single‐crystal OLEDs exhibit a maximum luminance of 50,170 cd/m2 and a peak EQE of 8.78%, which are better than DPA‐based devices. Furthermore, BSB‐Me single‐crystal HTLs with favorable interfacial properties enable large‐area OLEDs with uniform EL emission over the whole light‐emitting area of 1 mm × 1 mm. Interfacial properties of organic single‐crystal HTLs are investigated and verified to be vital to EL performances of single‐crystal OLEDs. High‐performance single‐crystal OLEDs can be realized with a peak EQE of 8.78% and a large functional area of up to 1 mm2. This work paves the way toward high‐performance organic single‐crystalline optoelectronic devices.

Methylammonium bismuth (III) iodide single crystals and films have been developed and investigated. We have further presented the first demonstration of using this organic–inorganic bismuth-based material to replace lead/tin-based perovskite materials in solution-processable solar cells. The organic–inorganic bismuth-based material has advantages of non-toxicity, ambient stability, and low-temperature solution-processability, which provides a promising solution to address the toxicity and stability challenges in organolead- and organotin-based perovskite solar cells. We also demonstrated that trivalent metal cation-based organic–inorganic hybrid materials can exhibit photovoltaic effect, which may inspire more research work on developing and applying organic-inorganic hybrid materials beyond divalent metal cations (Pb (II) and Sn (II)) for solar energy applications.

Ni3Al-based superalloys have excellent mechanical properties which have been widely used in civilian and military fields. In this study, the mechanical properties of the face-centred cubic structure Ni3Al were investigated by a first principles study based on density functional theory (DFT), and the generalized gradient approximation (GGA) was used as the exchange-correlation function. The bulk modulus, Young’s modulus, shear modulus and Poisson’s ratio of Ni3Al polycrystal were calculated by Voigt-Reuss approximation method, which are in good agreement with the existing experimental values. Moreover, directional dependences of bulk modulus, Young’s modulus, shear modulus and Poisson’s ratio of Ni3Al single crystal were explored. In addition, the thermodynamic properties (e.g., Debye temperature) of Ni3Al were investigated based on the calculated elastic constants, indicating an improved accuracy in this study, verified with a small deviation from the previous experimental value.

P2-type layered oxide, Na 2/3 Ni 1/3 Mn 2/3 O 2 , has drawn particular interest as a promising cathode material for sodium-ion batteries (SIBs) due to its fast sodium-ion transport channels with low migration potential. However, some catastrophic flaws, such as air instability, complicated multiphase evolution, and irreversible anionic redox, limit its electrochemical performance and hinder its application. Here, an air-stable single-crystal P2-type Na 2/3 Ni 1/3 Mn 1/3 Ti 1/3 O 2 is proposed based on the multifunctional structural modulation of Ti substitution that could alleviate the issues for practical SIBs. As a result, the cathode with high energy density shows excellent air stability and highly reversible phase transitions (P2-OP4), and delivers faster kinetics and stable anion redox chemistry. Meanwhile, a thorough investigation of the relationship between structure, function, and properties is demonstrated, emphasizing formation processes, electrochemical behavior, structural evolution, and air stability. Overall, this study provides the direction of multifunctional structural modulation for the development of high-performance sodium-based layered cathode materials for practical applications.