On the thermodynamics of plasticity during quasi-isentropic compression of metallic glass

Entropy production in quasi-isentropic compression (QIC) is critically important for understanding the properties of materials under extremeconditions. However, the origin and accurate quantification of entropy in this situation remain long-standing challenges. In this work, a framework is established for the quantification of entropy production and partition, and their relation to microstructural change in QIC. Cu50Zr50is taken as a model material, and its compression is simulated by molecular dynamics. On the basis of atomistic simulation-informed physicalproperties and free energy, the thermodynamic path is recovered, and the entropy production and its relation to microstructural change aresuccessfully quantified by the proposed framework. Contrary to intuition, entropy production during QIC of metallic glasses is relativelyinsensitive to the strain rate ˙γ when ˙γ ranges from 7.5 × 10^(8) to 2 × 10^(9)/s, which are values reachable in QIC experiments, with a magnitudeof the order of 10^(−2)kB/atom per GPa. However, when ˙γ is extremely high (>2 × 10^(9)/s), a notable increase in entropy production rate with˙γ is observed. The Taylor–Quinney factor is found to vary with strain but not with strain rate in the simulated regime. It is demonstrated thatentropy production is dominated by the configurational part, compared with the vibrational part. In the rate-insensitive regime, the increase inconfigurational entropy exhibits a linear relation to the Shannon-entropic quantification of microstructural change, and a stretched exponential relation to the Taylor–Quinney factor. The quantification of entropy is expected to provide thermodynamic insights into the fundamentalrelation between microstructure evolution and plastic dissipation.

Strain‑Induced Surface Interface Dual Polarization Constructs PML‑Cu/Bi_(12)O_(17)Br_(2) High‑Density Active Sites for CO_(2) Photoreduction

The insufficient active sites and slow interfacial charge trans-fer of photocatalysts restrict the efficiency of CO_(2) photoreduction.The synchronized modulation of the above key issues is demanding and chal-lenging.Herein,strain-induced strategy is developed to construct the Bi–O-bonded interface in Cu porphyrin-based monoatomic layer(PML-Cu)and Bi_(12)O_(17)Br_(2)(BOB),which triggers the surface interface dual polarization of PML-Cu/BOB(PBOB).In this multi-step polarization,the built-in electric field formed between the interfaces induces the electron transfer from con-duction band(CB)of BOB to CB of PML-Cu and suppresses its reverse migration.Moreover,the surface polarization of PML-Cu further promotes the electron converge in Cu atoms.The introduction of PML-Cu endows a high density of dispersed Cu active sites on the surface of PBOB,significantly promoting the adsorption and activation of CO_(2) and CO desorption.The conversion rate of CO_(2) photoreduction to CO for PBOB can reach 584.3μmol g-1,which is 7.83 times higher than BOB and 20.01 times than PML-Cu.This work offers valuable insights into multi-step polarization regulation and active site design for catalysts.

Trunk‑Inspired SWCNT‑Based Wrinkled Films for Highly‑Stretchable Electromagnetic Interference Shielding and Wearable Thermotherapy

Nowadays,the increasing electromagnetic waves generated by wearable devices are becoming an emerging issue for human health,so stretchable electromagnetic interference(EMI)shielding materials are highly demanded.Elephant trunks are capable of grabbing fragile vegetation and tearing trees thanks not only to their muscles but also to their folded skins.Inspired by the wrinkled skin of the elephant trunks,herein,we propose a winkled conductive film based on single-walled carbon nanotubes(SWCNTs)for multifunctional EMI applications.The conductive film has a sandwich structure,which was prepared by coating SWCNTs on both sides of the stretched elastic latex cylindrical substrate.The shrinking-induced winkled conductive network could withstand up to 200%tensile strain.Typically,when the stretching direction is parallel to the polarization direction of the electric field,the total EMI shielding effectiveness could surprisingly increase from 38.4 to 52.7 dB at 200%tensile strain.It is mainly contributed by the increased connection of the SWCNTs.In addition,the film also has good Joule heating performance at several voltages,capable of releasing pains in injured joints.This unique property makes it possible for strain-adjustable multifunctional EMI shielding and wearable thermotherapy applications.

Towards the Same Line of Liquid–Liquid Phase Transition of Dense Hydrogen from Various Theoretical Predictions

For a long time,there have been huge discrepancies between different models and experiments concerning the liquid-liquid phase transition(LLPT)in dense hydrogen.We present the results of extensive calculations of the LLPT in dense hydrogen using the most expensive first-principle path-integral molecular dynamics simulations available.The nonlocal density functional rVV10 and the hybrid functional PBEO are used to improve the description of the electronic structure of hydrogen.Of all the density functional theory calculations available,we report the most consistent results through quantum Monte Carlo simulations and coupled electron-ion Monte Carlo simulations of the LLPT in dense hydrogen.The critical point of the first-order LLPT is estimated to be above 2000 K according to the equation of state.Moreover,the metallization pressure obtained from the jump of dc electrical conductivity almost coincides with the plateau of equation of state.

Lattice Thermal Conductivity of MgSiO_(3) Perovskite and Post-Perovskite under Lower Mantle Conditions Calculated by Deep Potential Molecular Dynamics

Lattice thermal conductivity(κlat)of MgSiO_(3) perovskite and post-perovskite is an important parameter for the thermal dynamics in the Earth.Here,we develop a deep potential of density functional theory quality under entire thermodynamic conditions in the lower mantle,and calculate theκlatby the Green-Kubo relation.Deep potential molecular dynamics captures full-order anharmonicity and considers ill-defined phonons in low-κlatmaterials ignored in the phonon gas model.Theκlatshows negative temperature dependence and positive linear pressure dependence.Interestingly,theκlatundergos an increase at the phase boundary from perovskite to post-perovskite.We demonstrate that,along the geotherm,theκlatincreases by 18.2% at the phase boundary.Our results would be helpful for evaluating Earth’s thermal dynamics and improving the Earth model.

Measurement and correlation of solubility of 9-fluorenone in 11 pure organic solvents from T = 283.15 to 323.15 K

In this work, the solubility data of 9-fluorenone in 11 pure solvents(methanol, ethanol, n-propanol, isopropanol, n-butanol, iso-butanol, acetonitrile, ethyl formate, ethyl acetate, dimethyl sulfoxide, n-hexane)were measured by the gravimetric method from 278.15 K to 318.15 K under atmospheric pressure. The results showed that the solubility of 9-fluorenone in all tested solvents increased with the raised temperature. The solubility data were correlated by the modified Apelblat equation, λh model and NRTL(nonradom two fluid) model. The average relative deviation(ARD) correlated by three thermodynamic models in different solvents was all below 5%, which indicated that the three thermodynamic models fit the solubility data well. Furthermore, the mixing thermodynamic properties of 9-fluorenone in pure solvent systems were calculated via NRTL model. The results indicated the dissolution process of 9-fluorenone is spontaneous and entropically favorable. The solubility and the mixing thermodynamic properties provided in this paper would play an important role in industrial manufacture and follow-up operation of 9-fluorenone.

Structural transition dynamics of the formation of warm dense gold: From an atomic scale view

With the highly optimized embedded-atom-method(EAM)potential and electron-phonon coupling factor obtained from experimental data,the dynamics of the formation of warm dense gold and the nuclear response of gold foils upon intense laser excitation were investigated using two-temperature molecular dynamics simulations.Considering laser energy densities ranging from 0.18 to 1.17 MJ/kg,we provide a microscopic picture of the formation of warm dense gold.A threshold(0.19 MJ/kg)for the laser energy density was determined,identifying two different melting mechanisms.For an energy density below 0.19 MJ/kg,the melting of the foil is controlled by the propagation of melt fronts from external surfaces,which results in heterogeneous melting on the time scale of hundreds of picoseconds.For an energy density above 0.19 MJ/kg,homogeneous nucleation and growth of liquid regions inside the foil play the leading role,and homogeneous melting occurs with several picoseconds.Compared with previous simulations and experimental measurements,the evaluated different threshold value indicates that the improvement in the electron heat capacity for the two-temperature model by including the kinetic information of electrons may predict better laser-matter interactions under such extreme non-equilibrium conditions.

Tracking and recognition algorithm for a robot harvesting oscillating apples

Apple fruits on trees tend to swing because of wind or other natural causes,therefore reducing the accuracy of apple picking by robots.To increase the accuracy and to speed up the apple tracking and identifying process,tracking and recognition method combined with an affine transformation was proposed.The method can be divided into three steps.First,the initial image was segmented by Otsu’s thresholding method based on the two times Red minus Green minus Blue(2R-G-B)color feature;after improving the binary image,the apples were recognized with a local parameter adaptive Hough circle transformation method,thus improving the accuracy of recognition and avoiding the long,time-consuming process and excessive fitted circles in traditional Hough circle transformation.The process and results were verified experimentally.Second,the Shi-Tomasi corners detected and extracted from the first frame image were tracked,and the corners with large positive and negative optical flow errors were removed.The affine transformation matrix between the two frames was calculated based on the Random Sampling Consistency algorithm(RANSAC)to correct the scale of the template image and predict the apple positions.Third,the best positions of the target apples within 1.2 times of the prediction area were searched with a de-mean normalized cross-correlation template matching algorithm.The test results showed that the running time of each frame was 25 ms and 130 ms and the tracking error was more than 8%and 20%in the absence of template correction and apple position prediction,respectively.In comparison,the running time of our algorithm was 25 ms,and the tracking error was less than 4%.Therefore,test results indicate that speed and efficiency can be greatly improved by using our method,and this strategy can also provide a reference for tracking and recognizing other oscillatory fruits.

Light-induced irreversible structural phase transition in trilayer graphene

A crystal structure has a profound influence on the physical properties of the corresponding material.By synthesizing crystals with particular symmetries,one can strongly tune their properties,even for the same chemical configuration(compare graphite and diamond,for instance).Even more interesting opportunities arise when the structural phases of crystals can be changed dynamically through external stimulations.Such abilities,though rare,lead to a number of exciting phenomena,such as phase-change memory effects.In the case of trilayer graphene,there are two common stacking configurations(ABA and ABC)that have distinct electronic band structures and exhibit very different behaviors.Domain walls exist in the trilayer graphene with both stacking orders,showing fascinating new physics such as the quantum valley Hall effect.Extensive efforts have been dedicated to the phase engineering of trilayer graphene.However,the manipulation of domain walls to achieve precise control of local structures and properties remains a considerable challenge.Here,we experimentally demonstrate that we can switch from one structural phase to another by laser irradiation,creating domains of different shapes in trilayer graphene.The ability to control the position and orientation of the domain walls leads to fine control of the local structural phases and properties of graphene,offering a simple but effective approach to create artificial two-dimensional materials with designed atomic structures and electronic and optical properties.

Full-scale ab initio simulations of laser-driven atomistic dynamics

The coupling of excited states and ionic dynamics is the basic and challenging point for the materials response at extreme conditions.In the laboratory,the intense laser produces transient nature and complexity with highly nonequilibrium states,making it extremely difficult and interesting for both experimental measurements and theoretical methods.With the inclusion of laser-excited states,we extend an ab initio method into the direct simulations of whole laser-driven microscopic dynamics from solid to liquid.We construct the framework of combining the electron-temperature-dependent deep neural-network potential energy surface with a hybrid atomistic-continuum approach,controlling non-adiabatic energy exchange and atomistic dynamics,which enables consistent interpretation of experimental data.By large-scale ab initio simulations,we demonstrate that the nonthermal effects introduced by hot electrons play a dominant role in modulating the lattice dynamics,thermodynamic pathway,and structural transformation.We highlight that the present work provides a path to realistic computational studies of laser-driven processes,thus bridging the gap between experiments and simulations.

Dynamic landscape mapping of humoral immunity to SARS-CoY-2 identifies non-structural protein antibodies associated with the survival of critical COVID-19 patients

A comprehensive analysis of the humoral immune response to the severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)is essential in understanding COVID-19 pathogenesis and developing antibody-based diagnostics and therapy.In this work,we performed a longitudinal analysis of antibody responses to SARS-CoV-2 proteins in 104 serum samples from 49 critical COVID-19 patients using a peptide-based SARS-CoV-2 proteome microarray.Our data show that the binding epitopes of IgM and IgG antibodies differ across SARS-CoV-2 proteins and even within the same protein.

Interaction-induced topological transition in spin-orbit coupled ultracold bosons

Recent experiments in ultracold atoms have reported the realization of quantum anomalous Hall phases in spin-orbit coupled systems.Motivated by such advances,we investigate spin-orbit coupled Bose-Bose mixtures in a two-dimensional square optical Raman lattice.Complete phase diagrams are obtained via a nonperturbative real-space bosonic dynamical mean-field theory.Various quantum phases are predicted,including Mott phases with z-ferromagnetic,xy-antiferromagnetic and vortex textures,and superfluid phases with the exotic spin orders,induced by the competition between the lattice hopping and spin-orbit coupling.To explain the underlying physics in the Mott regime,an efective Hamiltonian is derived based on second-order perturbation theory,where pseudospin order stems from the interplay of efective Dzyaloshinskii-Moriya superexchange and Heisenberg interactions.In the presence of the Zeeman field,the competition of strong interaction and Zeeman energy facilitates a topological phase,which is confirmed both by the nontrivial topological Bott index and spectral function with topological edge states.Our work indicates that spin-orbit coupling can induce rich non-Abelian topological physics in strongly correlated ultracold atomic systems.