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Lead-free bilayer heterometallic halide perovskite with reversible phase transition and photoluminescence properties

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Chinese Chemical Letters 2023年第4期34卷 590-594页

作者： Qiangqiang Jia Ting Shao Liang Tong Changyuan Su Dawei Fu Haifeng Lu Institute for Science and Applications of Molecular Ferroelectrics Key Laboratory of the Ministry of Education for Advanced Catalysis MaterialsZhejiang Normal UniversityJinhua 321004China Ordered Matter Science Research Center Jiangsu Key Laboratory for Science and Applications of Molecular FerroelectricsSoutheast UniversityNanjing 211189China School of Environment and Chemical Engineering Jiangsu University of Science and TechnologyZhenjiang 212002China

The layered heterometallic halide perovskites, as a newly explored material, have attracted great scientific attention. As one of the representatives of perovskite, lead-free or lead-substituted perovskite materials are widely applied in photovoltaic, sensors, catalysis, detectors and other fields. Therefore, it is urgent to carry out more systematic exploration and expand applicable preresearch, so as to make more interesting discoveries in this new hot spot. As an interesting candidate, heterometallic compounds will introduce more structural adjustability and novel physical properties, which is the main feature to be selected as the research hotspot. Here, we reported a lead-free bilayer heterometallic Ruddlesden-Popper(RP) type perovskite, [(MACH)_(2)CsAgBiBr_(7)](MACH = cyclohexanemethylamine), which possesses a reversible phase transition at 379.6 K/375.1 K during heating-cooling cycle. Besides, it exhibits reddish-brown light emission under 365 nm, meanwhile, CIE chromaticity coordinate is(0.32, 0.45) on the yellow side and correlated color temperature is about 6000 K. Moreover, both the experimental data and theoretical calculation results suggest that [(MACH)_(2)CsAgBiBr_(7)] shows indirect semiconducting characteristics. In summary, this work will inspire the design of lead-free heterometallic perovskite materials for the application of sensors and light-emitting diodes(LEDs) fields.

关键词： Lead-free Heterometallic Perovskite phase transition Photoluminescence

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Employing halogen-halogen interaction to construct high-temperature hybrid perovskite phase transition materials

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Chinese Chemical Letters 2023年第6期34卷 521-524页

作者： Dongying Fu Zuoming Hou Zhuo Chen Yueyue He Xian-Ming Zhang Institute of Crystalline Materials Shanxi UniversityTaiyuan 030006China State Key Laboratory of Quantum Optics and Quantum Optics Devices Shanxi UniversityTaiyuan 030006China

Organic-inorganic hybrid perovskites(OIHPs)materials with high phase transition temperature(T_(p))have been widely studied in the field of molecular switches,solar energy and electric power.At present,the OIHPs with high T_(p)are generally constructed through molecular design,which can be applied to a wide temperature range.Here,three one-dimensional(1D)OIHPs[R-Cl EQ]PbCl_(3)(T_(p)=442 K),[R-Cl EQ]PbBr_(3)(T_(p)=499 K)and[R-Cl EQ]PbI_(3)(T_(p)above m.p.)(R-Cl EQ=(R)-N-chloroethyl-3-quinuclidinol)with different T_(p)are obtained by regulating the halogen-halogen interaction and hydrogen bonding in the system.Especially in[R-Cl EQ]Pb X_(3)(X=Cl,Br and I)crystal system,all the halogen bonds tend to form at approximately 180°angles and the strength of halogen bonding is found to be increased from 1.59×10^(-3)Hartree to 2.35×10^(-3)Hartree with increased atom number from Cl to I.The synergistic effect of halogen bonding and hydrogen bonding provide a useful strategy for the design OIHPs phase transition materials with high T_(p).

关键词： Halogen-halogen interaction phase transition Hybrid perovskite Molecular designing

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Tunable phase transition, band gap and SHG properties by halogen replacement of hybrid perovskites [(thiomorpholinium)PbX_(3), X = Cl,Br,I]

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Chinese Chemical Letters 2022年第2期33卷 1032-1036页

作者： Simin Liu Lei He Yuzhen Wang Pingping Shi Qiong Ye Jiangsu Key Laboratory for Science and Applications of Molecular Ferroelectrics and School of Chemistry and Chemical Engineering Southeast UniversityNanjing 211189China

By the replacement of halogen anion,three new multifunctional organic-inorganic hybrid perovskites(thiomorpholinium)PbX_(3)(X=Cl,Br,I)were successfully synthesized and underwent reversible struc-tural transformation above room temperature,accompanied by the anomalous change of dielectric con-stant.With the adjustment of the halogen anion from Cl to I in the inorganic skeleton,the space group is transformed from centrosymmetric space group P2_(1)/c((thiomorpholinium)PbCl_(3))to chiral one P2_(1)2_(1)2_(1)((thiomorpholinium)PbBr3,(thiomorpholinium)PbI_(3))at room temperature.The ordered-disordered tran-sition of organic cations and the change of hydrogen bonds with the increase of temperature lead to above-room-temperature phase transitions.Ultraviolet absorption and second-harmonic generation(SHG)measurements confirmed that both the band gap and SHG activity of(thiomorpholinium)PbX_(3)(X=Cl,Br,I)crystals were tunable.The band gaps reveal a broadening trend with 3.532 e V,3.410 e V and 3.175 e V along the Cl→Br→I series.This work provides an effective molecular design for multifunctional organic-inorganic perovskites.

关键词： phase transition Band gap Nonlinear optical Organic-inorganic hybrid perovskite Halogen replacement

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Discontinuous phase diagram of amorphous carbons

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National Science Review 2024年第4期11卷 164-171页

作者： YinBo Zhu ZhouYu Fang ZhongTing Zhang HengAn Wu CAS Key Laboratory of Mechanical Behavior and Design of Materials Department of Modern MechanicsUniversity of Science and Technology of China State Key Laboratory of Nonlinear Mechanics Institute of Mechanics Chinese Academy of Sciences

The short-range order and medium-range order of amorphous carbons demonstrated in experiments allow us to rethink whether there exist intrinsic properties hidden by atomic disordering. Here we presented six representative phases of amorphous carbons（0.1–3.4 g/cm3）, namely, disordered graphene network（DGN）, high-density amorphous carbon（HDAC）, amorphous diaphite（a-DG）, amorphous diamond（a-D）, paracrystalline diamond（p-D）, and nano-polycrystalline diamond（NPD）, respectively, classified by their topological features and microstructural characterizations that are comparable with experiments. To achieve a comprehensive physical landscape for amorphous carbons, a phase diagram was plotted in the sp3/sp2versus density plane, in which the counterintuitive discontinuity originates from the inherent difference in topological microstructures, further guiding us to discover a variety of phase transitions among different amorphous carbons. Intriguingly, the power law, log（sp3/sp2） ∝ ρn, hints at intrinsic topology and hidden order in amorphous carbons, providing an insightful perspective to reacquaint atomic disorder in non-crystalline carbons.

关键词： amorphous carbons disordered carbons phase diagram microstructural topology phase transition

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Reversible phase transition for switchable second harmonic generation in 2D perovskite microwires

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SmartMat 2022年第4期3卷 657-667页

作者： Yingjie Zhao Jiahui Zhao Yangwu Guo Jinjin Zhao Jiangang Feng Yue Geng Junchuan Yang Hanfei Gao Meng Yuan Lei Jiang Yuchen Wu Key Laboratory of Bio-Inspired Materials and Interfacial Science Technical Institute of Physics and ChemistryChinese Academy of SciencesBeijingChina School of Future Technology University of Chinese Academy of SciencesBeijingChina Ji Hua Laboratory FoshanChina Department of Chemical and Biomolecular Sciences National University of SingaporeSingaporeSingapore

Highly efficient second-harmonic generation(SHG)has facilitated the development of nanophotonics and sustained promising applications,ranging from electro-optical modulation,frequency conversion,and optical frequency combs to pulse characterization.Although controllable SHG switching has been observed in nanophotonics structures and molecule systems,the relatively small SHG switching contrast impedes its application in switchable nonlinear optics.Herein,reversible phase transitions between glassy and crystalline states without material degradation are demonstrated based on solution-processed chiral perovskite microwire arrays.Breaking of lattice inversion symmetry and high crystallinity support efficient SHG in microwire arrays.By synergy of high-performance SHG and reversible phase transitions between glassy and crystalline states,reversible switching of SHG is demonstrated under facile conditions.The high SHG switching performances,together with a small footprint,pave the way toward the integration of switchable nonlinear devices based on microwire arrays.

关键词： 2D chiral perovskites assembled microwires nonlinear optics phase transition second harmonic generation

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phase transition of DNA compaction in confined space: Effects of macromolecular crowding are dominant

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Chinese Physics B 2020年第1期29卷 489-494页

作者：陈尔坤范洋涛赵光菊毛宗良周海平刘艳辉 College of Physics Guizhou UniversityGuiyang 550025China Collaborative Innovation Center for Optoelectronic Semiconductors and Efficient Devices Pen-Tung Sah Institute of Micro-Nano Science and TechnologyXiamen UniversityXiamen 361005China Department of Computer Science and Engineering Shaoxing UniversityShaoxing 312000China

With a view of detecting the effects of macromolecular crowding on the phase transition of DNA compaction confined in spherical space,Monte Carlo simulations of DNA compaction in free space,in confined spherical space without crowders and in confined spherical space with crowders were performed separately.The simulation results indicate that macromolecular crowding effects on DNA compaction are dominant over the roles of multivalent counterions.In addition,effects of temperature on the phase transition of DNA compaction have been identified in confined spherical space with different radii.In confined spherical space without crowders,the temperature corresponding to phase transition depends on the radius of the confined spherical space linearly.In contrast,with the addition of crowders to the confined spherical space,effects of temperature on the phase transition of DNA compaction become insignificant,whereas the phase transition at different temperatures strongly depends on the size of crowder,and the critical volume fraction of crowders pertains to the diameter of crowder linearly.

关键词： macromolecular crowding Monte Carlo simulation DNA compaction phase transition

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phase transition of shocked water up to 6 GPa:Transmittance investigation

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Chinese Physics B 2021年第5期30卷 287-292页

作者：吴浪任月虹廖文强黄曦晨刘福生张明建孙燕云 Key Laboratory of Advanced Technologies of Materials Ministry of Education of ChinaSchool of Physical Science and TechnologySouthwest Jiaotong UniversityChengdu 610031China Sichuan Provincial Key Laboratory(for Universities)of High Pressure Science and Technology Southwest Jiaotong UniversityChengdu 610031China

The phase transition behaviors of the shocked water are investigated by employing an optical transmittance in-situ detection system.Based on the light scattering theory and phase transformation kinetics,the phase transition mechanism of the water under multiple shocks is discussed.The experimental data indicate that the evolution of the transmittance of the shocked water can be broadly divided into three stages:relaxation stage,decline stage,and recovery stage.In the early stage of the phase transition,the new phase particles began to form around the quartz/window interface.It should be mentioned that the water/ice phase boundary seems to move toward the liquid region in one experiment of this work.Due to the new phase core being much smaller than the wavelength of the incident light,the transmittance of the sample within the relaxation stage remains steady.The decline stage can be divided into the rapid descent stage and the slow descent stage in this work,which is considered as the different growth rates of the new phase particle under different shock loadings.The recovery stage is attributed to the emergence of the new phase particles which are bigger than the critical value.However,the influence of the size growth and the population growth of the new phase particles on the transmittance restrict each other,which may be responsible for the phenomenon that the transmittance curve does not return to the initial level.

关键词： phase transition shocked water multiple compresses transmittance scattering

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phase transition, elastic and electronic properties of topological insulator Sb_2Te_3 under pressure: First principle study

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Chinese Physics B 2016年第2期25卷 348-354页

作者：卢清张怀勇程艳陈向荣姬广富 Institute of Atomic and Molecular Physics College of Physical Science and TechnologySichuan University Key Laboratory of High Energy Density Physics and Technology of Ministry of Education College of Physical Science and TechnologySichuan University National Key Laboratory of Shock Wave and Detonation Physics Institute of Fluid PhysicsChinese Academy of Engineering Physics

The phase transition, elastic and electronic properties of three phases（phase Ⅰ,Ⅱ, and Ⅲ） of Sb_2Te_3 are investigated by using the generalized gradient approximation（GGA） with the PBESOL exchange–correlation functional in the framework of density-functional theory. Some basic physical parameters, such as lattice constants, bulk modulus, shear modulus,Young＇s modulus, Poisson＇s ratio, acoustic velocity, and Debye temperature Θ are calculated. The obtained lattice parameters under various pressures are consistent with experimental data. phase transition pressures are 9.4 GPa（Ⅰ→Ⅱ） and 14.1 GPa（Ⅱ→Ⅲ）, which are in agreement with the experimental results. According to calculated elastic constants, we also discuss the ductile or brittle characters and elastic anisotropies of three phases. phases Ⅰ and Ⅲ are brittle, while phaseⅡ is ductile. Of the three phases, phaseⅡ has the most serious degree of elastic anisotropy and phase Ⅲ has the slightest one.Finally, we investigate the partial densities of states（PDOSs） of three phases and find that the three phases possess some covalent features.

关键词： Sb2Ze3 phase transition elastic properties electronic properties

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phase transition,structural and thermodynamic properties of Mg_2 Si polymorphs

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Chinese Physics B 2011年第3期20卷 101-109页

作者：余本海陈东 College of Physics and Electronic Engineering Xinyang Normal University

The plane-wave pseudo-potential method within the framework of first principles is used to investigate the structural and elastic properties of Mg2Si in its intermediate pressure （Pnma） and high pressure phases （P63/mrnc）. The lattice constants, the band structures. The bulk moduli of the Mg2Si polymorphs are presented and discussed. The phase transition from anti-cotunnite to Ni2In-type Mg2Si is successfully reproduced using a vibrational Debye-like model. The phase boundary can be described as P = 24.02994 ＋ 3.93 × 10^-3T -- 4.66816 × 10^-5T2 -- 2.2501 × 10^-9T3＋ 2.33786 × 10^-11T4. To complete the fundamental characteristics of these polymorphs we have analysed thermodynamic properties, such as thermal expansion and heat capacity, in a pressure range of 1-40 GPa and a temperature range of 0-1300 K. The obtained results tend to support the available experimental data and other theoretical results. Therefore, the present results indicate that the combination of first principles and a vibrational Debye-like model is an efficient scheme to simulate the high temperature behaviours of Mg2Si.

关键词： semiconductors thermodynamic properties phase transition band structure

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phase transition on speed limit traffic with slope

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Chinese Physics B 2008年第8期17卷 3014-3020页

作者：李兴莉宋涛邝华戴世强 Shanghai Institute of Applied Mathematics and Mechanics Shanghai University College of Physics and Electronic Engineering Guangxi Normal University

Through introducing a generalized optimal speed function to consider spatial position, slope grade and variable safe headway, the effect of slope in a single-lane highway on the traffic flow is investigated with the extended optimal speed model. The theoretical analysis and simulation results show that the flux of the whole road with the upgrade （or downgrade） increases linearly with density, saturates at a critical density, then maintains this saturated value in a certain density range and finally decreases with density. The value of saturated flux is equal to the maximum flux of the upgrade （or downgrade） without considering the slight influence of the driver＇s sensitivity. And the fundamental diagrams also depend on sensitivity, slope grade and slope length. The spatiotemporal pattern gives the segregation of different traffic phases caused by the rarefaction wave and the shock wave under a certain initial vehicle number. A comparison between the upgrade and the downgrade indicates that the value of saturated flux of the downgrade is larger than that of the upgrade under the same condition. This result is in accordance with the real traffic.

关键词： generalized optimal speed car-following model slope phase transition

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