The insulator-to-metal transition in VO2 has garnered extensive attention for its potential applications in ultrafast switches, neuronal network architectures, and storage technologies. However, the photoinduced insulator-to-metal transition remains controversial, especially whether a complete structural transformation from the monoclinic to rutile phase is necessary. Here we employ the real-time time-dependent density functional theory to track the dynamic evolution of atomic and electronic structures in photoexcited VO2, revealing the emergence of a long-lived monoclinic metal phase under low electronic excitation. The emergence of the metal phase in the monoclinic structure originates from the dissociation of the local V-V dimer, driven by the self-trapped and self-amplified dynamics of photoexcited holes, rather than by an electron-electron correction. On the other hand, the monoclinic-to-rutile phase transition does appear at higher electronic excitation. Our findings validate the existence of monoclinic metal phase and provide a comprehensive picture of the insulator-to-metal transition in photoexcited VO2.

The photoinduced semiconductor-to-metal transition (PSMT) unveils crucial photodynamic mechanisms and holds great promise for information storage, sensing, optoelectronics, optical switches, etc. All previously reported PSMTs have occurred between two structural phases of the same material, lacking real-space evidence at the atomic or molecular level. Herein, we report atomic-scale observations of a photoinduced 'face changing': light irradiation transforms a semiconductor copper selenide (Cu2Se) surface layer on Cu(111) into a well-defined metallic Cu layer. Se atoms sink to form a new Cu2Se sublayer, while the original subsurface Cu atoms are lifted to the top layer. The Cu2Se-to-Cu transition barrier is significantly lower in the excited state compared to the ground state. Thermoactivation enables the reverse transition. The photoinduced Cu2Se-to-Cu and thermoactivated Cu-to-Cu2Se transitions are highly reversible. This work, which demonstrates PSMT between two distinct materials and photo-driven interlayer atom migration, unlocks an unconventional and intriguing route for PSMT and surface modification technologies.

A significant limitation of wide-band-gap materials is their low hole mobility related to localized holes with heavy effective masses (m & lowast;h). We identify in low-symmetric wide-band-gap compounds an anion-anion antibonding coupling (AAAC) effect as the intrinsic factor behind hole localization, which explains the extremely heavy m & lowast;h and self-trapped hole (STH) formation observed in gallium oxide (,8-Ga2O3). We propose a design principle for achieving light holes by manipulating AAAC, demonstrating that specific strain conditions can reduce m & lowast;h in ,8-Ga2O3 along c & lowast; from 4.77 m0 to 0.38 m0, making it comparable to the electron mass (0.28 m0) while also slightly suppressing the formation of self-trapped holes, evidenced by the reduction in the formation energy of hole polarons from -0.57 to -0.45 eV under tensile strain. The light holes show significant anisotropy, potentially enabling two-dimensional transport in bulk material. This study provides a fundamental understanding of hole mass enhancement and STH formation in novel wide-band-gap materials and suggests new pathways for engineering hole mobilities.

VO2 experiences a transition from an insulating monoclinic phase to a metallic rutile phase near room temperature, which can be triggered by photoexcitation. This unique phenomenon highlights the significant potential of VO2 in optoelectronic applications. However, the photoinduced shape deformation, also known as photostriction, which occurs during this phase transition has been largely overlooked. Here, we present findings on the photostriction of VO2 ceramics and investigate the impact of photoinduced phase transition on its photostriction behavior. Large photostriction exceeding 0.1% is achievable in VO2 ceramics when illuminated by both 405 and 655 nm monochromatic laser. In contrast to the majority of inorganic photostrictive materials, VO2 demonstrates a nonlinear increase in photostriction as light intensity increases. Upon surpassing the threshold light intensity, the photo-triggered M-to-R phase transition leads to an anomalous increase, approximately 40%, in photostriction. Furthermore, the photoexcited structural evolution and the variation in photostrictive response to different light wavelengths are also depicted by ab initio molecular dynamics simulations. This study not only demonstrates VO2 as an excellent inorganic material for photo-actuating applications, but also validates the effectiveness of utilizing photoinduced phase transition to explore high-performance inorganic photostrictive materials.

The insulator-to-metal transition (IMT) in vanadium dioxide (VO2) has garnered extensive attention for its potential applications in ultrafast switches, neuronal network architectures, and storage technologies. However, a significant controversy persists regarding the formation of the IMT, specifically concerning whether a complete structural phase transition from monoclinic (M1) to rutile (R) phase is necessary. Here we employ the real-time time-dependent density functional theory (rt-TDDFT) to track the dynamic evolution of atomic and electronic structures in photoexcited VO2, revealing the emergence of a long-lived monoclinic metal phase (MM) under low electronic excitation. The emergence of the metal phase in the monoclinic structure originates from the dissociation of the local V-V dimer, driven by the self-trapped and self-amplified dynamics of photoexcited holes, rather than by a pure electron-electron correction. On the other hand, the M1-to-R phase transition does appear at higher electronic excitation. Our findings validate the existence of MM phase and provide a comprehensive picture of the IMT in photoexcited VO2.

Solar wind charge exchange（SWCX） is the process of solar wind high-valence ions exchanging charges with neutral components and generating soft X-rays.Recently,detecting the SWCX emission from the magnetosphere is proposed as a new technique to study the magnetosphere using panoramic soft X-ray imaging.To better prepare for the data analysis of upcoming magnetospheric soft X-ray imaging missions,this paper compares the magnetospheric SWCX emission obtained by two methods in an XMM-Newton observation,during which the solar wind changed dramatically.The two methods differ in the data used to fit the diffuse X-ray background（DXB） parameters in spectral analysis.The method adding data from the ROSAT All-Sky Survey（RASS） is called the RASS method.The method using the quiet observation data is called the Quiet method,where quiet observations usually refer to observations made by the same satellite with the same target but under weaker solar wind conditions.Results show that the spectral compositions of magnetospheric SWCX emission obtained by the two methods are very similar,and the changes in intensity over time are highly consistent,although the intensity obtained by the RASS method is about 2.68±0.56 keV cm -2 s -1 sr -1 higher than that obtained by the Quiet method.Since the DXB intensity obtained by the RASS method is about 2.84±0.74 keV cm -2 s -1 sr -1 lower than that obtained by the Quiet method,and the linear correlation coefficient between the difference of SWCX and DXB obtained by the two methods in diffe rent energy band is close to-1,the diffe rences in magnetospheric SWCX can be fully attributed to the diffe rences in the fitted DXB.The difference between the two methods is most significant when the energy is less than 0.7 keV,which is also the main energy band of SWCX emission.In addition,the difference between the two methods is not related to the SWCX intensity and,to some extent,to solar wind conditions,because SWCX intensity typically va ries with the solar wind.In summary,both methods are robust and reliable,and should be considered based on the best available options.

Lithium-ion capacitors（LICs） combining the advantages of lithium-ion batteries and supercapacitors are considered a promising nextgeneration energy storage device. However, the sluggish kinetics of battery-type anode cannot match the capacitor-type cathode, restricting the development of LICs. Herein, hierarchical carbon framework（HCF） anode material composed of 0D carbon nanocage bridged with 2D graphene network are developed via a template-confined synthesis process. The HCF with nanocage structure reduces the Li + transport path and benefits the rapid Li + migration, while 2D graphene network can promote the electron interconnecting of carbon nanocages. In addition, the doped N atoms in HCF facilitate to the adsorption of ions and enhance the pseudo contribution, thus accelerate the kinetics of the anode. The HCF anode delivers high specific capacity, remarkable rate capability. The LIC pouch-cell based on HCF anode and active HCF（a-HCF） cathode can provide a high energy density of 162 Wh kg -1 and a superior power density of 15.8 kW kg -1 , as well as a long cycling life exceeding 15,000cycles. This study demonstrates that the well-defined design of hierarchical carbon framework by incorporating 0D carbon nanocages and 2D graphene network is an effective strategy to promote LIC anode kinetics and hence boost the LIC electrochemical performance.

Star-forming galaxies (SFGs) adhere to a surprisingly tight scaling relation of dust attenuation parameterized by the infrared excess (IRX=$L_{\rm IR}/L_{\rm UV}$), being jointly determined by the star formation rate (SFR), galaxy size ($R_{\rm e}$), metallicity ($Z$/Z$_\odot$) and axial ratio ($b/a$). We examine how these galaxy parameters determine the effective dust attenuation and give rise to the universal IRX relation, utilizing a simple two-component star-dust geometry model in which dust in the dense and diffuse interstellar medium (ISM) follows exponential mass density profiles, connected with but not necessarily identical to the stellar mass profiles. Meanwhile, empirical relations are adopted to link galaxy properties, including the gas--star formation relation, the dust-to-stellar size relation, as well as the dust-to-gas ratio versus metallicity relation. By fitting a large sample of local SFGs with the model, we obtain the best-fitting model parameters as a function of metallicity, showing that the two-component geometry model is able to successfully reproduce the dependence of IRX on SFR, $R_{\rm e}$, $b/a$ at given $Z$/Z$_\odot$, as well as the dependence of power-law indices on metallicity. Moreover, we also retrieve constraints on the model geometry parameters, including the optical depth of birth clouds (BCs), BC-to-total dust mass fraction, BC covering factor of UV-emitting stars, and star-to-total dust disc radius ratio, which all evolve with galaxy metallicity. Finally, a consistent picture of how the star-dust geometry in SFGs evolves with galaxy metallicity is discussed.

ABSTRACT Strong AGN heating provides an alternative means for the disruption of cluster cool cores (CCs) to cluster mergers. In this work, we present a systematic Chandra study of a sample of 108 nearby (z < 0.1) galaxy clusters, to investigate the effect of AGN heating on CCs. About 40 per cent of clusters with small offsets between the BCG and the X-ray centre (≤50 kpc) have small CCs. For comparison, 14 of 17 clusters with large offsets have small CCs, which suggests that mergers or sloshing can be efficient in reducing the CC size. Relaxed, small CC clusters generally have weak radio AGNs ($P_{1.4\rm GHz}\lt 10^{23}$ W Hz−1), and they show a lack of systems hosting a radio AGN with intermediate radio power ($2\times 10^{23}\lt P_{1.4\rm GHz}\lt 2\times 10^{24}$ W Hz−1). We found that the strongest circumnuclear (<1 kpc) X-ray emission only exists in clusters with strong radio AGN. The duty cycle of relaxed, small CC clusters is less than half of that for large CC clusters. It suggests that the radio activity of BCGs is affected by the properties of the surrounding gas beyond the central ∼10 kpc, and strong radio AGNs in small X-ray CCs fade more rapidly than those embedded in large X-ray CCs. A scenario is also presented for the transition of large CCs and coronae due to radio AGN feedback. We also present a detailed analysis of galaxy cluster 3C 129.1 as an example of a CC remnant possibly disrupted by radio AGN.

Na3LuB8O15, the first sodium lutetium borate in the Na-Lu-B-O system, was prepared by the spontaneous crystallization method. Na3LuB8O15 is crystallized in the centrosymmetric triclinic space group P (1) over bar with the following cell parameters: a = 6.4047(12)angstrom, b = 7.3342(13)angstrom, c = 13.081(2)angstrom, alpha = 88.999(7)degrees, beta = 78.631(8)degrees, gamma = 66.622(7)degrees, and Z = 2. The general configuration of Na3LuB8O15 can be characterized as a network structure created by infrequent multiboron anion chain skeletons [B8O17] and [LuO7] polyhedra shared by oxygen atoms, where Na ions are filled in the pores to balance charges. According to a UV-vis-NIR spectrum investigation, the chemical has a short ultraviolet cutoff edge (185 nm). Thermal analysis reveals incongruent melting compound properties. In addition, a first-principles calculation was conducted to delve deeper into the correlation between the performance and the structure.

Dust attenuation in star-forming galaxies (SFGs), as parameterized by the infrared excess (IRX ≡ L_ IR/L_ UV), is found to be tightly correlated with star formation rate (SFR), metallicity and galaxy size, following a universal IRX relation up to z=3. This scaling relation can provide a fundamental constraint for theoretical models to reconcile galaxy star formation, chemical enrichment, and structural evolution across cosmic time. We attempt to reproduce the universal IRX relation over 0.1≤ z≤ 2.5 using the EAGLE hydrodynamical simulations and examine sensitive parameters in determining galaxy dust attenuation. Our findings show that while the predicted universal IRX relation from EAGLE approximately aligns with observations at z≤ 0.5, noticeable disparities arise at different stellar masses and higher redshifts. Specifically, we investigate how modifying various galaxy parameters can affect the predicted universal IRX relation in comparison to the observed data. We demonstrate that the simulated gas-phase metallicity is the critical quantity for the shape of the predicted universal IRX relation. We find that the influence of the infrared luminosity and infrared excess is less important while galaxy size has virtually no significant effect. Overall, the EAGLE simulations are not able to replicate some of the observed characteristics between IRX and galaxy parameters of SFGs, emphasizing the need for further investigation and testing for our current state-of-the-art theoretical models.

Herein, a new Cd-based telluride Ba4Cd2Ge2Te9 was successfully synthesized and characterized, which was first identified in the Ba-Cd-Ge-Te system. It crystallizes in the Pbcm space group and its structure features infinite [Cd2Ge2Te9]8- chains, with Ba2+ filling in the interstitial space to balance the charge. The fluorescence spectrum indicates that the title compound generates purple-emission the range of 415-459 nm under the 300 nm excitation, with a peak lifetime of about 1.18 ns at 436 nm. In addition, first-principles calculations show that Ba4Cd2Ge2Te9 has a birefringence of 0.298 @ 2090 nm, which is determined by the superposition of the polarization of the terminal Te atom and Ge2Te6 unit. Thermoelectricity measurements show that the title compound possesses a large Seebeck coefficient (655 mu V K-1 @300 K) and a low thermal conductivity (0.87 W m-1 K-1 @300 K).

Characterizing the structural properties of galaxies in high-redshift protoclusters is key to our understanding of the environmental effects on galaxy evolution in the early stages of galaxy and structure formation. In this study, we assess the structural properties of 85 and 87 Halpha emission-line candidates (HAEs) in the densest regions of two massive protoclusters, BOSS1244 and BOSS1542, respectively, using HST H-band imaging data. Our results show a true pair fraction of 22+-5 (33+-6) percent in BOSS1244 (BOSS1542), which yields a merger rate of 0.41+-0.09 (0.52+-0.04) per Gyr for massive HAEs with log (M_*/M_sun) > 10.3. This rate is 1.8 (2.8) times higher than that of the general fields at the same epoch. Our sample of HAEs exhibits half-light radii and Sersic indices that cover a broader range than field star-forming galaxies. Additionally, about 15 percent of the HAEs are as compact as the most massive (log(M_*/M_sun) > 11) spheroid-dominated population. These results suggest that the high galaxy density and cold dynamical state (i.e., velocity dispersion of <400 km/s) are key factors that drive galaxy mergers and promote structural evolution in the two protoclusters. Our findings also indicate that both the local environment (on group scales) and the global environment play essential roles in shaping galaxy morphologies in protoclusters. This is evident in the systematic differences observed in the structural properties of galaxies between BOSS1244 and BOSS1542.

We present here the analysis of X-rays point sources detected in several observations available in the XMM-Newton public archive. We focused, in particular, on energies below 1 keV, which are of particular relevance to the understanding of the Diffuse X-ray Background. The average field of all the exposures is 0.09 deg^-2. We reached an average flux sensitivity of 5.8x10^-16 erg s^-1 cm^-2 in the soft band (0.5-2.0 keV) and 2.5x10^-16 erg s^-1 cm^-2 in the very soft band (0.4-0.6 keV). In this paper we discuss the logN-logS results, the contribution to the integrated X-ray sky flux, and the properties of the cumulative spectrum from all sources. In particular, we found an excess flux at around 0.5 keV in the composite spectrum of faint sources. The excess seems to be a general property of all the fields observed suggesting an additional class of weak sources is contributing to the X-ray emission at these energies. Combining our results with previous investigations we have also quantified the contribution of the individual components of the diffuse X-ray Background in the 3/4 keV band.

Under photoirradiation, inorganic photostrictive materials undergo a unidirectional deformation (mainly expansion), resulting in tiny strains one to two orders of magnitude smaller than the electric field-driven strains. Here, we report an unprecedented bidirectional deformation under photoirradiation in inorganic solid Pb3V2O8, showing expansion (up to 0.01%) at low photoexcitation and, at high photoexcitation, becoming contracted with compressive strain over 0.4%, comparable to electric field-induced strains. We find that the expansion at low photoexcitation is prompted by photoinduced thermal and nonthermal expansion owing to the elongation of Pb–O bonds driven by photoexcitation-generated interatomic force, whereas the contraction at high photoexcitation with a much larger strain is driven by the V dimerization via an electron-lattice self-amplification process when the photoexcitation-generated V–O interatomic force overwhelms the Pb–O interatomic force. These findings provide a promising candidate with more degrees of freedom for photoactuation and also open a new avenue to design photostrictive materials.

Birefringent crystals are essential in the domains of linear and nonlinear optics that need light wave polarization control. Rare earth borate has become a popular study material for ultraviolet (UV) birefringence crystals due to its short cutoff edge in the UV area. RbBaScB6O12, a two-dimensional layered structure compound with the B3O6 group, was effectively synthesized through spontaneous crystallization. The UV cutoff edge of RbBaScB6O12 is shorter than 200 nm, and the experimental birefringence is 0.139 @ 550 nm. Theoretical research indicates that the large birefringence originates from the synergistic impact of the B3O6 group and the ScO6 octahedron. RbBaScB6O12 is an outstanding candidate material for birefringence crystals in the UV and even deep UV regions due to its short UV cutoff edge and significant birefringence.

Chalcogenides are promising candidates for exploring mid- and far-infrared nonlinear optical (NLO) materials. Nevertheless, although tellurides possess greater advantages in the above-mentioned spectral regions, the reports on telluride NLO materials are far fewer than those on sulfides and selenides. In this work, a new quaternary NLO-active telluride, KCd4Ga5Te12, was discovered, and its Rb and Cs analogues were successfully synthesized. They are crystallized in the trigonal R3 space group and the structure features a 3D diamond-like framework constructed by vertex- sharing asymmetric MTe4 tetrahedra (centered by disordered Cd and Ga) that are stacked along the c-axis. Moreover, a comprehensive study of their IR NLO properties, photoluminescence properties, and structural features was performed. These compounds exhibited large powder second-harmonic generation (SHG) intensities, about 2.1 (2.7, 4.4) times that of AgGaSe2 in the particle size range of 20-50 (125-150) mu m and a wide transmission range (similar to 25 mu m). The SHG-density analysis revealed that the largest component chi((2))(333) of KCd4Ga5Te12 originates from three types of Te in the crystal structure. More importantly, it is rare in literature to demonstrate the consistency of linear and NLO properties calculated using both ultrasoft pseudopotentials and norm-conservation pseudopotentials. Besides, the title compounds also exhibit strong luminescence emissions around 420 and 470 nm at 298 K. This work implies that title compounds are promising candidates in the IR NLO applications.

Nonlinear optical (NLO) crystals, being the primary medium for laser wavelength conversion, are crucial in all-solid-state lasers. Borophosphates offer more structural varieties than pure borates and phosphates, and they have become popular as NLO crystal candidates. Through spontaneous crystallization, we acquired a noncentrosymmetric alkali metal borophosphate crystal material, K2Na3B2P3O13 (KNBPO). KNBPO crystallizes in the orthorhombic Cmc21 space group with the following unit cell parameters: a = 13.9238(18) Å, b = 6.7673(8) Å, c = 12.1298(15) Å, and Z = 4, and its structure is characterized by a fundamental building unit 1∞ [B2P3O13] chain structure made up of bridging oxygen linkages between BO4 and PO4 tetrahedra. KNBPO has a short ultraviolet (UV) cut-off edge (<186 nm), a congruent melting characteristic, good thermal stability, and a moderate second harmonic generation response roughly 0.42 times that of KH2PO4. Theoretical calculations reveal that the optical properties of the compound mainly originate from BO4 and PO4 units. Due to the short UV cut-off edge, KNBPO can be used as a potential NLO material in the UV and even deep UV regions, and it enhances the structural variety of borophosphates, which has a reference value for scholars investigating similar materials.

This Perspective focuses on recent advances in understanding ultrafast processes involved in photoinduced structural phase transitions and proposes a strategy for precise manipulation of such transitions. It has been demonstrated that photoexcited carriers occupying empty antibonding or bonding states generate atomic driving forces that lead to either stretching or shortening of associated bonds, which in turn induce collective and coherent motions of atoms and yield structural transitions. For instance, phase transitions in IrTe2 and VO2, and nonthermal melting in Si, can be explained by the occupation of specific local bonding or antibonding states during laser excitation. These cases reveal the electronic-orbital-selective nature of laser-induced structural transitions. Based on this understanding, we propose an inverse design protocol for achieving or preventing a target structural transition by controlling the related electron occupations with orbital-selective photoexcitation. Overall, this Perspective provides a comprehensive overview of recent advancements in dynamical structural control in solid materials.

The Hot Universe Baryon Surveyor (HUBS) is a proposed space-based X-ray telescope for detecting X-ray emissions from the hot gas content in our universe. With its unprecedented spatially-resolved high-resolution spectroscopy and large field of view, the HUBS mission will be uniquely qualified to measure the physical and chemical properties of the hot gas in the interstellar medium, the circumgalactic medium, the intergalactic medium, and the intracluster medium. These measurements will be valuable for two key scientific goals of HUBS, namely to unravel the AGN and stellar feedback physics that governs the formation and evolution of galaxies, and to probe the baryon budget and multi-phase states from galactic to cosmological scales. In addition to these two goals, the HUBS mission will also help us solve some problems in the fields of galaxy clusters, AGNs, diffuse X-ray backgrounds, supernova remnants, and compact objects. This paper discusses the perspective of advancing these fields using the HUBS telescope.