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Published in last 1 year |  In last 2 years |  In last 3 years |  All Please wait a minute... For selected: Download citations EndNote Ris BibTeX Toggle thumbnails Select Residual stress modeling of mitigated fused silica damage sites with CO2 laser annealing Chuanchao Zhang(张传超), Wei Liao(廖威), Lijuan Zhang(张丽娟), Xiaolong Jiang(蒋晓龙), Zhenhua Fang(方振华), and Xiaodong Jiang(蒋晓东) Chin. Phys. B, 2024, 33 (3): 036101.   DOI: 10.1088/1674-1056/acf447 Abstract （29）   HTML （0）    PDF （1306KB）（21）       Knowledge map    A numerical model based on measured fictive temperature distributions is explored to evaluate the residual stress fields of CO2 laser-annealed mitigated fused silica damage sites. The proposed model extracts the residual strain from the differences in thermoelastic contraction of fused silica with different fictive temperatures from the initial frozen-in temperatures to ambient temperature. The residual stress fields of mitigated damage sites for the CO2 laser-annealed case are obtained by a finite element analysis of equilibrium equations and constitutive equations. The simulated results indicate that the proposed model can accurately evaluate the residual stress fields of laser-annealed mitigated damage sites with a complex thermal history. The calculated maximum hoop stress is in good agreement with the reported experimental result. The estimated optical retardance profiles from the calculated radial and hoop stress fields are consistent with the photoelastic measurements. These results provide sufficient evidence to demonstrate the suitability of the proposed model for describing the residual stresses of mitigated fused silica damage sites after CO2 laser annealing. Select Photostability of colloidal single photon emitter in near-infrared regime at room temperature Si-Yue Jin(靳思玥) and Xing-Sheng Xu(许兴胜) Chin. Phys. B, 2024, 33 (3): 036102.   DOI: 10.1088/1674-1056/ad1090 Abstract （21）   HTML （0）    PDF （1344KB）（26）       Knowledge map    The photostability of a colloidal single photon emitter in near-infrared regime at room temperature is investigated. The fluorescence lifetime, blinking phenomenon, and anti-bunching effect of a single CdTeSe/ZnS quantum dot with an emission wavelength of 800 nm at room temperature are studied. The second-order correlation function at zero delay time is much smaller than 0.1, which proves that the emission from single quantum dots at 800 nm is a highly pure single-photon source. The effects of the irradiation duration on the fluorescence from single quantum dots are analyzed. The experimental results can be explained by a recombination model including a multi-nonradiative recombination center model and a multi-charged model. Select Electronic effects on radiation damage in α-iron: A molecular dynamics study Lin Jiang(江林), Min Li(李敏), Bao-Qin Fu(付宝勤), Jie-Chao Cui(崔节超), and Qing Hou(侯氢) Chin. Phys. B, 2024, 33 (3): 036103.   DOI: 10.1088/1674-1056/ad0ec4 Abstract （26）   HTML （0）    PDF （2935KB）（25）       Knowledge map    Iron (Fe)-based alloys, which have been widely used as structural materials in nuclear reactors, can significantly change their microstructure properties and macroscopic properties under high flux neutron irradiation during operation, thus, the problems associated with the safe operation of nuclear reactors have been put forward naturally. In this work, a molecular dynamics simulation approach combined with electronic effects is developed for investigating the primary radiation damage process in α-Fe. Specifically, the influence of electronic effects on the collision cascade in Fe is systematically evaluated based on two commonly used interatomic potentials for Fe. The simulation results reveal that both electronic stopping (ES) and electron-phonon coupling (EPC) can contribute to the decrease of the number of defects in the thermal spike phase. The application of ES reduces the number of residual defects after the cascade evolution, whereas EPC has a reverse effect. The introduction of electronic effects promotes the formation of the dispersive subcascade: ES significantly changes the geometry of the damaged region in the thermal spike phase, whereas EPC mainly reduces the extent of the damaged region. Furthermore, the incorporation of electronic effects effectively mitigates discrepancies in simulation outcomes when using different interatomic potentials. Select Molecular dynamics study of primary radiation damage in TiVTa concentrated solid-solution alloy Yong-Peng Zhao(赵永鹏), Yan-Kun Dou(豆艳坤), Xin-Fu He(贺新福), Han Cao(曹晗),Lin-Feng Wang(王林枫), Hui-Qiu Deng(邓辉球), and Wen Yang(杨文) Chin. Phys. B, 2024, 33 (3): 036104.   DOI: 10.1088/1674-1056/ad0146 Abstract （33）   HTML （0）    PDF （807KB）（29）       Knowledge map    The primary radiation damage in pure V and TiVTa concentrated solid-solution alloy (CSA) was studied using a molecular dynamics method. We have performed displacement cascade simulations to explore the generation and evolution behavior of irradiation defects. The results demonstrate that the defect accumulation and agglomeration in TiVTa CSA are significantly suppressed compared to pure V. The peak value of Frenkel pairs during cascade collisions in TiVTa CSA is much higher than that in pure V due to the lower formation energy of point defects. Meanwhile, the longer lifetime of the thermal spike relaxation and slow energy dissipation capability of TiVTa CSA can facilitate the recombination of point defects. The defect agglomeration rate in TiVTa CSA is much lower due to the lower binding energy of interstitial clusters and reduced interstitial diffusivity. Furthermore, the occurrence probability of dislocation loops in TiVTa CSA is lower than that in pure V. The reduction in primary radiation damage may enhance the radiation resistance of TiVTa CSA, and the improved radiation tolerance is primarily attributed to the relaxation stage and long-term defect evolution rather than the ballistic stage. These results can provide fundamental insights into irradiation-induced defects evolution in refractory CSAs. Select Comparative study on phase transition behaviors of fractional molecular field theory and random-site Ising model Ting-Yu Liu(刘婷玉), Wei Zhao(赵薇), Tao Wang(王涛), Xiao-Dong An(安小冬), Lai Wei(卫来), and Yi-Neng Huang(黄以能) Chin. Phys. B, 2024, 33 (3): 036403.   DOI: 10.1088/1674-1056/ad0cc7 Abstract （39）   HTML （1）    PDF （725KB）（23）       Knowledge map    Fractional molecular field theory (FMFT) is a phenomenological theory that describes phase transitions in crystals with randomly distributed components, such as the relaxor-ferroelectrics and spin glasses. In order to verify the feasibility of this theory, this paper fits it to the Monte Carlo simulations of specific heat and susceptibility versus temperature of two-dimensional (2D) random-site Ising model (2D-RSIM). The results indicate that the FMFT deviates from the 2D-RSIM significantly. The main reason for the deviation is that the 2D-RSIM is a typical system of component random distribution, where the real order parameter is spatially heterogeneous and has no symmetry of space translation, but the basic assumption of FMFT means that the parameter is spatially uniform and has symmetry of space translation. Select Theoretical characterization of the adsorption configuration of pyrrole on Si(100) surface by x-ray spectroscopy Hao-Qing Li(李好情), Jing Ming(明静), Zhi-Ang Jiang(姜志昂), Hai-Bo Li(李海波), Yong Ma(马勇), and Xiu-Neng Song(宋秀能) Chin. Phys. B, 2024, 33 (2): 026102.   DOI: 10.1088/1674-1056/aceaeb Abstract （55）   HTML （0）    PDF （1061KB）（10）       Knowledge map    The possible configurations of pyrrole absorbed on a Si(100) surface have been investigated by x-ray photoelectron spectroscopy (XPS) and near-edge x-ray absorption fine structure (NEXAFS) spectra. The C-1s XPS and NEXAFS spectra of these adsorption configurations have been calculated by using the density functional theory (DFT) method and full-core hole (FCH) approximation to investigate the relationship between the adsorption configurations and the spectra. The result shows that the XPS and NEXAFS spectra are structurally dependent on the configurations of pyrrole absorbed on the Si(100) surface. Compared with the XPS, the NEXAFS spectra are relatively sensitive to the adsorption configurations and can accurately identify them. The NEXAFS decomposition spectra produced by non-equivalent carbon atoms have also been calculated and show that the spectral features vary with the diverse types of carbon atoms and their structural environments. Select Floquet spectrum and universal dynamics of a periodically driven two-atom system Wenzhu Xie(谢文柱), Zhengqiang Zhou(周正强), Xuan Li(李轩), Simiao Cui(崔思淼), and Mingyuan Sun(孙明远) Chin. Phys. B, 2024, 33 (2): 026702.   DOI: 10.1088/1674-1056/ad0623 Abstract （64）   HTML （2）    PDF （28513KB）（59）       Knowledge map    We investigate the Floquet spectrum and excitation properties of a two-ultracold-atom system with periodically driven interaction in a three-dimensional harmonic trap. The interaction between the atoms is changed by varying the s-wave scattering length in two ways, the cosine and the square-wave modulations. It is found that as the driving frequency increases, the Floquet spectrum exhibits two main features for both modulations, the accumulating and the spreading of the quasienergy levels, which further lead to different dynamical behaviors. The accumulation is associated with collective excitations and the persistent growth of the energy, while the spread indicates that the energy is bounded at all times. The initial scattering length, the driving frequency and amplitude can all significantly change the Floquet spectrum as well as the dynamics. However, the corresponding relation between them is valid universally. Finally, we propose a mechanism for selectively exciting the system to one specific state by using the avoided crossing of two quasienergy levels, which could guide preparation of a desired state in experiments. Select Effect of surface modification on the radiation stability of diamond ohmic contacts Lian-Xi Mu(牟恋希), Shang-Man Zhao(赵上熳), Peng Wang(王鹏), Xiao-Lu Yuan(原晓芦), Jin-Long Liu(刘金龙), Zhi-Fu Zhu(朱志甫), Liang-Xian Chen(陈良贤), Jun-Jun Wei(魏俊俊), Xiao-Ping Ou-Yang(欧阳晓平), and Cheng-Ming Li(李成明) Chin. Phys. B, 2024, 33 (2): 026801.   DOI: 10.1088/1674-1056/ace61e Abstract （60）   HTML （0）    PDF （968KB）（43）       Knowledge map    The ohmic contact interface between diamond and metal is essential for the application of diamond detectors. Surface modification can significantly affect the contact performance and eliminate the interface polarization effect. However, the radiation stability of a diamond detector is also sensitive to surface modification. In this work, the influence of surface modification technology on a diamond ohmic contact under high-energy radiation was investigated. Before radiation, the specific contact resistivities ($\rho_{\rm c}$) between Ti/Pt/Au-hydrogen-terminated diamond (H-diamond) and Ti/Pt/Au-oxygen-terminated diamond (O-diamond) were $2.0 \times 10^{-4}$ $\Omega \cdot $cm$^{2}$ and $4.3 \times 10^{-3}$ $\Omega \cdot $cm$^{2}$, respectively. After 10 MeV electron radiation, the $\rho_{\rm c}$ of Ti/Pt/Au H-diamond and Ti/Pt/Au O-diamond were $5.3 \times 10^{-3}$ $\Omega \cdot $cm$^{2}$ and $9.1 \times 10^{-3}$ $ \Omega \cdot $cm$^{2}$, respectively. The rates of change of $\rho_{\rm c}$ of H-diamond and O-diamond after radiation were 2550% and 112%, respectively. The electron radiation promotes bond reconstruction of the diamond surface, resulting in an increase in $\rho_{\rm c}$. Select Growth and characterization of Bi(110)/CrTe2 heterostructures: Exploring interplay between magnetism and topology Zhenyu Yuan(袁震宇), Fazhi Yang(杨发枝), Baiqing Lv(吕佰晴), Yaobo Huang(黄耀波), Tian Qian(钱天), Jinpeng Xu(徐金朋), and Hong Ding(丁洪) Chin. Phys. B, 2024, 33 (2): 026802.   DOI: 10.1088/1674-1056/ad082a Abstract （71）   HTML （3）    PDF （3637KB）（92）       Knowledge map    The interplay between topology and magnetism is vital for realizing exotic quantum phenomena, significant examples including quantum anomalous Hall effect, axion insulators, and high-order topological states. These states host great potential for future applications in high-speed and low-consumption electronic devices. Despite being extensively investigated, practical platforms are still scarce. In this work, with molecular beam epitaxy (MBE), we provide the first experimental report on high-quality Bi(110)/CrTe$_{2}$ magnetic heterostructure. By employing in-situ high-resolution scanning tunneling microscopy, we are able to examine the interaction between magnetism and topology. There is a potential edge state at an energy level above the Fermi level, but no edge states observed near the Fermi level The absence of high-order topological corner states near $E_{\rm F}$ highlights the importance of lattice matching and interface engineering in designing high-order topological states. Our study provides key insights into the interplay between two-dimensional magnetic and topological materials and offers an important dimension for engineering magnetic topological states. Select Sensitivity investigation of 100-MeV proton irradiation to SiGe HBT single event effect Ya-Hui Feng(冯亚辉), Hong-Xia Guo(郭红霞), Yi-Wei Liu(刘益维), Xiao-Ping Ouyang(欧阳晓平), Jin-Xin Zhang(张晋新), Wu-Ying Ma(马武英), Feng-Qi Zhang(张凤祁), Ru-Xue Bai(白如雪), Xiao-Hua Ma(马晓华), and Yue Hao(郝跃) Chin. Phys. B, 2024, 33 (1): 016104.   DOI: 10.1088/1674-1056/acf303 Abstract （63）   HTML （0）    PDF （2002KB）（12）       Knowledge map    The single event effect (SEE) sensitivity of silicon—germanium heterojunction bipolar transistor (SiGe HBT) irradiated by 100-MeV proton is investigated. The simulation results indicate that the most sensitive position of the SiGe HBT device is the emitter center, where the protons pass through the larger collector-substrate (CS) junction. Furthermore, in this work the experimental studies are also carried out by using 100-MeV proton. In order to consider the influence of temperature on SEE, both simulation and experiment are conducted at a temperature of 93 K. At a cryogenic temperature, the carrier mobility increases, which leads to higher transient current peaks, but the duration of the current decreases significantly. Notably, at the same proton flux, there is only one single event transient (SET) that occurs at 93 K. Thus, the radiation hard ability of the device increases at cryogenic temperatures. The simulation results are found to be qualitatively consistent with the experimental results of 100-MeV protons. To further evaluate the tolerance of the device, the influence of proton on SiGe HBT after gamma-ray (60Coγ) irradiation is investigated. As a result, as the cumulative dose increases, the introduction of traps results in a significant reduction in both the peak value and duration of the transient currents. Select Effect of grain size on gas bubble evolution in nuclear fuel: Phase-field investigations Dan Sun(孙丹), Qingfeng Yang(杨青峰), Jiajun Zhao(赵家珺), Shixin Gao(高士鑫), Yong Xin(辛勇), Yi Zhou(周毅), Chunyu Yin(尹春雨), Ping Chen(陈平), Jijun Zhao(赵纪军), and Yuanyuan Wang(王园园) Chin. Phys. B, 2024, 33 (1): 016105.   DOI: 10.1088/1674-1056/ad08a6 Abstract （65）   HTML （0）    PDF （5537KB）（44）       Knowledge map    Numerous irradiation-induced gas bubbles are created in the nuclear fuel during irradiation, leading to the change of microstructure and the degradation of mechanical and thermal properties. The grain size of fuel is one of the important factors affecting bubble evolution. In current study, we first predict the thermodynamic behaviors of point defects as well as the interplay between vacancy and gas atom in both UO2 and U3Si2 according to ab initio approach. Then, we establish the irradiation-induced bubble phase-field model to investigate the formation and evolution of intra- and inter-granular gas bubbles. The effects of fission rate and temperature on the evolutions of bubble morphologies in UO2 and U3Si2 have been revealed. Especially, a comparison of porosities under different grain sizes is examined and analyzed. To understand the thermal conductivity as functions of grain size and porosity, the heat transfer capability of U3Si2 is evaluated. Select Simulation of space heavy-ion induced primary knock-on atoms in bipolar devices Bin Zhang(张彬), Hao Jiang(姜昊), Xiao-Dong Xu(徐晓东), Tao Ying(应涛), Zhong-Li Liu(刘中利), Wei-Qi Li(李伟奇), Jian-Qun Yang(杨剑群), and Xing-Ji Li(李兴冀) Chin. Phys. B, 2024, 33 (1): 016106.   DOI: 10.1088/1674-1056/acd3e1 Abstract （68）   HTML （0）    PDF （7552KB）（20）       Knowledge map    Bipolar junction transistors (BJTs) are often used in spacecraft due to their excellent working characteristics. However, the complex space radiation environment induces primary knock-on atoms (PKAs) in BJTs through collisions, resulting in hard-to-recover displacement damage and affecting the performance of electronic components. In this paper, the properties of PKAs induced by typical space heavy ions (C, N, O, Fe) in BJTs are investigated using Monte Carlo simulations. The simulated results show that the energy spectrum of ion-induced PKAs is primarily concentrated in the low-energy range (17 eV—100 eV) and displays similar features across all tested ions. The PKAs induced by the collision of energetic ions have large forward scattering angles, mainly around 88°. Moreover, the distribution of PKAs within a transistor as a function of depth displays a peak characteristic, and the peak position is linearly proportional to the incident energy at a certain energy range. These simulation outcomes serve as crucial theoretical support for long-term semiconductor material defect evolution and ground testing of semiconductor devices. Select Hamiltonian system for the inhomogeneous plane elasticity of dodecagonal quasicrystal plates and its analytical solutions Zhiqiang Sun(孙志强), Guolin Hou(侯国林), Yanfen Qiao(乔艳芬), and Jincun Liu (刘金存) Chin. Phys. B, 2024, 33 (1): 016107.   DOI: 10.1088/1674-1056/acfaf3 Abstract （67）   HTML （0）    PDF （706KB）（16）       Knowledge map    A Hamiltonian system is derived for the plane elasticity problem of two-dimensional dodecagonal quasicrystals by introducing the simple state function. By using symplectic elasticity approach, the analytic solutions of the phonon and phason displacements are obtained further for the quasicrystal plates. In addition, the effectiveness of the approach is verified by comparison with the data of the finite integral transformation method. Select Linear magnetoresistance and structural distortion in layered SrCu4-xP2 single crystals Yong Nie(聂勇), Zheng Chen(陈正), Wensen Wei(韦文森), Huijie Li(李慧杰), Yong Zhang(张勇), Ming Mei(梅明), Yuanyuan Wang(王园园), Wenhai Song(宋文海), Dongsheng Song(宋东升), Zhaosheng Wang(王钊胜), Xiangde Zhu(朱相德), Wei Ning(宁伟), and Mingliang Tian(田明亮) Chin. Phys. B, 2024, 33 (1): 016108.   DOI: 10.1088/1674-1056/acf705 Abstract （72）   HTML （0）    PDF （1255KB）（98）       Knowledge map    We report a systematic study on layered metal SrCu4-xP2 single crystals via transport, magnetization, thermodynamic measurements and structural characterization. We find that the crystals show large linear magnetoresistance without any sign of saturation with a magnetic field up to 30 T. We also observe a phase transition with significant anomalies in resistivity and heat capacity at Tp ～ 140 K. Thermal expansion measurement reveals a subtle lattice parameter variation near Tp, i.e., ΔLc/Lc～ 0.062%. The structural characterization confines that there is no structure transition below and above Tp. All these results suggest that the nonmagnetic transition of SrCu4-xP2 could be associated with structural distortion. Select Geometries and electronic structures of ZrnCu(n =2-12) clusters: A joint machine-learning potential density functional theory investigation Yizhi Wang(王一志), Xiuhua Cui(崔秀花), Jing Liu(刘静), Qun Jing(井群), Haiming Duan(段海明), and Haibin Cao(曹海宾) Chin. Phys. B, 2024, 33 (1): 016109.   DOI: 10.1088/1674-1056/acd5c2 Abstract （68）   HTML （1）    PDF （3828KB）（24）       Knowledge map    Zr-based amorphous alloys have attracted extensive attention because of their large glassy formation ability, wide supercooled liquid region, high elasticity, and unique mechanical strength induced by their icosahedral local structures. To determine the microstructures of Zr—Cu clusters, the stable and metastable geometry of ZrnCu (n=2—12) clusters are screened out via the CALYPSO method using machine-learning potentials, and then the electronic structures are investigated using density functional theory. The results show that the ZrnCu (n≥ 3) clusters possess three-dimensional geometries, ZrnCu (n≥ 9) possess cage-like geometries, and the Zr12Cu cluster has icosahedral geometry. The binding energy per atom gradually gets enlarged with the increase in the size of the clusters, and ZrnCu (n=5, 7, 9, 12) have relatively better stability than their neighbors. The magnetic moment of most ZrnCu clusters is just 1μB, and the main components of the highest occupied molecular orbitals (HOMOs) in the Zr12Cu cluster come from the Zr-d state. There are hardly any localized two-center bonds, and there are about 20 σ-type delocalized three-center bonds. Select Temperature effect on nanotwinned Ni under nanoindentation using molecular dynamic simulation Xi He(何茜), Ziyi Xu(徐子翼), and Yushan Ni(倪玉山) Chin. Phys. B, 2024, 33 (1): 016201.   DOI: 10.1088/1674-1056/acf997 Abstract （72）   HTML （0）    PDF （5638KB）（17）       Knowledge map    Temperature effect on atomic deformation of nanotwinned Ni (nt-Ni) under localized nanoindentation is investigated in comparison with nanocrystalline Ni (nc-Ni) through molecular simulation. The nt-Ni exhibits enhanced critical load and hardness compared to nc-Ni, where perfect, stair-rod and Shockley dislocations are activated at $(1\bar{1}1)$, $(\bar{1}11)$ and $(11\bar{1})$ slip planes in nt-Ni compared to only Shockley dislocation nucleation at $(1\bar{1}1)$ and $(\bar{1}11)$ slip planes of nc-Ni. The nt-Ni exhibits a less significant indentation size effect in comparison with nc-Ni due to the dislocation slips hindrance of the twin boundary. The atomic deformation associated with the indentation size effect is investigated during dislocation transmission. Different from the decreasing partial slips parallel to the indenter surface in nc-Ni with increasing temperature, the temperature-dependent atomic deformation of nt-Ni is closely related to the twin boundary: from the partial slips parallel to the twin boundary (~10 K), to increased confined layer slips and decreased twin migration(300 K—600 K), to decreased confined layer slips and increased dislocation interaction of dislocation pinning and dissociation (900 K—1200 K). Dislocation density and atomic structure types through quantitative analysis are implemented to further reveal the above-mentioned dislocation motion and atomic structure alteration. Our study is helpful for understanding the temperature-dependent plasticity of twin boundary in nanotwinned materials. Select Atomistic evaluation of tension—compression asymmetry in nanoscale body-centered-cubic AlCrFeCoNi high-entropy alloy Runlong Xing(邢润龙) and Xuepeng Liu(刘雪鹏) Chin. Phys. B, 2024, 33 (1): 016202.   DOI: 10.1088/1674-1056/acfc37 Abstract （67）   HTML （0）    PDF （7171KB）（31）       Knowledge map    The tension and compression of face-centered-cubic high-entropy alloy (HEA) nanowires are significantly asymmetric, but the tension--compression asymmetry in nanoscale body-centered-cubic (BCC) HEAs is still unclear. In this study, the tension--compression asymmetry of the BCC AlCrFeCoNi HEA nanowire is investigated using molecular dynamics simulations. The results show a significant asymmetry in both the yield and flow stresses, with BCC HEA nanowire stronger under compression than under tension. The strength asymmetry originates from the completely different deformation mechanisms in tension and compression. In compression, atomic amorphization dominates plastic deformation and contributes to the strengthening, while in tension, deformation twinning prevails and weakens the HEA nanowire. The tension--compression asymmetry exhibits a clear trend of increasing with the increasing nanowire cross-sectional edge length and decreasing temperature. In particular, the compressive strengths along the [001] and [111] crystallographic orientations are stronger than the tensile counterparts, while the [110] crystallographic orientation shows the exactly opposite trend. The dependences of tension--compression asymmetry on the cross-sectional edge length, crystallographic orientation, and temperature are explained in terms of the deformation behavior of HEA nanowire as well as its variations caused by the change in these influential factors. These findings may deepen our understanding of the tension--compression asymmetry of the BCC HEA nanowires. Select Determining Hubbard U of VO2 by the quasi-harmonic approximation Longjuan Kong(孔龙娟), Yuhang Lu(陆雨航), Xinying Zhuang(庄新莹), Zhiyong Zhou(周志勇), and Zhenpeng Hu(胡振芃) Chin. Phys. B, 2024, 33 (1): 016302.   DOI: 10.1088/1674-1056/acfd18 Abstract （72）   HTML （0）    PDF （1284KB）（19）       Knowledge map    Vanadium dioxide VO2 is a strongly correlated material that undergoes a metal-to-insulator transition around 340 K. In order to describe the electron correlation effects in VO2, the DFT + U method is commonly employed in calculations. However, the choice of the Hubbard U parameter has been a subject of debate and its value has been reported over a wide range. In this paper, taking focus on the phase transition behavior of VO2, the Hubbard U parameter for vanadium oxide is determined by using the quasi-harmonic approximation (QHA). First-principles calculations demonstrate that the phase transition temperature can be modulated by varying the U values. The phase transition temperature can be well reproduced by the calculations using the Perdew—Burke—Ernzerhof functional combined with the U parameter of 1.5 eV. Additionally, the calculated band structure, insulating or metallic properties, and phonon dispersion with this U value are in line with experimental observations. By employing the QHA to determine the Hubbard U parameter, this study provides valuable insights into the phase transition behavior of VO2. The findings highlight the importance of electron correlation effects in accurately describing the properties of this material. The agreement between the calculated results and experimental observations further validates the chosen U value and supports the use of the DFT+U method in studying VO2. Select Effects of Mg-doping temperature on the structural and electrical properties of nonpolar a-plane p-type GaN films Kai Chen(陈凯), Jianguo Zhao(赵见国), Yu Ding(丁宇), Wenxiao Hu(胡文晓), Bin Liu(刘斌), Tao Tao(陶涛), Zhe Zhuang(庄喆), Yu Yan(严羽), Zili Xie(谢自力), Jianhua Chang(常建华), Rong Zhang(张荣), and Youliao Zheng(郑有炓) Chin. Phys. B, 2024, 33 (1): 016801.   DOI: 10.1088/1674-1056/acdc0b Abstract （85）   HTML （0）    PDF （872KB）（35）       Knowledge map    Nonpolar (11—20) a-plane p-type GaN films were successfully grown on r-plane sapphire substrate with the metal—organic chemical vapor deposition (MOCVD) system. The effects of Mg-doping temperature on the structural and electrical properties of nonpolar p-type GaN films were investigated in detail. It is found that all the surface morphology, crystalline quality, strains, and electrical properties of nonpolar a-plane p-type GaN films are interconnected, and are closely related to the Mg-doping temperature. This means that a proper performance of nonpolar p-type GaN can be expected by optimizing the Mg-doping temperature. In fact, a hole concentration of 1.3×1018 cm-3, a high Mg activation efficiency of 6.5%, an activation energy of 114 meV for Mg acceptor, and a low anisotropy of 8.3% in crystalline quality were achieved with a growth temperature of 990 ℃. This approach to optimizing the Mg-doping temperature of the nonpolar a-plane p-type GaN film provides an effective way to fabricate high-efficiency optoelectronic devices in the future. Select Structural stability and ion migration of Li2MnO3 cathode material under high pressures Ze-Ren Xie(谢泽仁), Si-Si Zhou(周思思), Bei-Bei He(贺贝贝), Huan-Wen Wang(王欢文), Yan-Sheng Gong(公衍生), Jun Jin(金俊), Xiang-Gong Zhang(张祥功), and Rui Wang(汪锐) Chin. Phys. B, 2023, 32 (12): 126101.   DOI: 10.1088/1674-1056/ace2b1 Abstract （77）   HTML （0）    PDF （1053KB）（58）       Knowledge map    Some special fields, such as deep-sea exploration, require batteries and their electrode materials to withstand extremely high pressure. As the cathode material has the highest energy density, Li-excess Mn-based materials are also likely to be utilized in such an environment. However, the effect of pressure on the crystal structure and migration barrier of this kind of material is still not clear at present. Therefore, in this study, we investigate the properties of the matrix material of Li-excess Mn-based material, Li2MnO3, under high pressure. The equation of state, bulk modulus, and steady-state volume of Li2MnO3 are predicted by the method of first principles calculation. The calculations of unit cells at different pressures reveal that the cell parameters suffer anisotropic compression under high pressure. During compression, Li-O bond is more easily compressed than Mn-O bond. The results from the climbing image nudged elastic band (CINEB) method show that the energy barrier of Li+ migration in the lithium layer increases with pressure increasing. Our study can provide useful information for utilizing Li-excess Mn-based materials under high pressure. page Page 1 of 88 Total 1751 records First page Prev page Next page Last page