检索结果-南通市图书馆

Chinese Physics B 2015年第10期24卷 400-407页

作者：张伟陈青云曾召益蔡灵仓 School of Science Southwest University of Science and Technology Laboratory for Shock Wave and Detonation Physics Research Institute of Fluid PhysicsChinese Academy of Engineering Physics School of National Defense Science and Technology Southwest University of Science and Technology College of Physics and Electronic Engineering Chongqing Normal University

We calculated the structural, elastic, and electronic properties of alkali metal Na atoms doped type-I silicon-clathrate compound（Na8Si46） under pressure using first-principles methods. The obtained dependencies of bond lengths and bond angles on pressure show heterogeneous behaviors which may bring out a structural transition. By using the elastic stability criteria from the calculated elastic constants, we confirm that the Na8Si46 is elastically unstable under high pressure. Some of the mechanical and thermal quantities include bulk modulus, shear modulus,Young＇s modulus, Debye temperature,sound velocity, melting point, and hardness, which are also derived from the elastic constants. The calculated total and partial electron densities of states of Na8Si46 indicate a weak interaction between the encapsulated Na atoms and the silicon framework. Moreover, the effect of pressure on its electronic structure is also investigated, which suggests that pressure is not a good choice to enhance the thermoelectricity performance of Na8Si46.

关键词： clathrate compound elastic constants electronic structure density functional theory

First principle calculation of elastic and thermodynamic properties of stishovite

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2010年第12期19卷 425-430页

作者：刘勋周显明曾召益 Laboratory for Shockwave and Detonation Physics Institute of Fluid PhysicsChina Academy of Engineering Physics College of Physical Science and Technology Sichuan University

Using ab initio plane-wave pseudo-potential density functional theory method, the elastic constants and band structures of stishovite were calculated. The calculated elastic constants under ambient conditions agree well with previous experimental and theoretical data. C13, C33, C44, and C66 increase nearly linearly with pressure while C11 and C12 show irregularly changes with pressure over 20 GPa. The shear modulus （Cll-C12）/2 was observed to decrease drastically between 40 GPa and 50 GPa, indicating acoustic mode softening in consistency with the phase transition to CaC12-type structure around 50 GPa. The calculated band structures show no obvious difference at 0 and 80 GPa, being consistent with the high incompressibility of stishovite. With a quasi-harmonic Debye model, thermodynamic properties of stishovite were also calculated and the results are in good agreement with available experimental data.

关键词： first principle elastic constants thermal properties quasi-harmonic Debye model

elastic and thermodynamic properties of vanadium nitride under pressure and the effect of metallic bonding on its hardness

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2014年第2期23卷 385-390页

作者：濮春英周大伟包代小卢成靳希联宿太超张飞武 College of Physics and Electronic Engineering Nanyang Normal University The School Hospital Nanyang Normal University State Key Laboratory of Superhard Materials College of PhysicsJilin University Institute of Materials Science and Engineering Henan Polytechnic University Nanochemistry Research Institute Curtin University

By the particle-swarm optimization method, it is predicted that tetragonal P42mc, 141md, and orthorhombic Amm2 phases of vanadium nitride （VN） are energetically more stable than NaCl-type structure at 0 K. The enthalpies of the predicted three new VN phases, along with WC, NaC1, AsNi, CsCl type structures, are calculated each as a function of pressure. It is found that VN exhibits the WC-to-CsCl type phase transition at 256 GPa. For the considered seven crystal- lographic VN phases, the structures, elastic constants, bulk moduli, shear moduli, and Debye temperatures are investigated. Our calculated equilibrium structural parameters are in very good agreement with the available experimental results and the previous theoretical results for the NaC1 phase. The Debye temperatures of VN predicted three novel phases, which are all higher than those of the remaining structures. The elastic constants, thermodynamic properties, and elastic anisotropies of VN under pressure are obtained and the mechanical stabilities are analyzed in detail based on the mechanical stability criteria. Moreover, the effect of metallic bonding on the hardness of VN is also investigated, which shows that VNs in P42mc, 141md, and Amm2 phases are potential superhard phases. Further investigation on the experimental level is highly recommended to confirm our calculations presented in this paper.

关键词： vanadium nitride elastic constants thermodynamic properties hardness

Ab initio calculations of the elastic,electronic,optical,and vibrational properties of PdGa compound under pressure

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2012年第9期21卷 422-429页

作者： H. Koc A. Yildirim E. Deligoz Department of Physics Siirt University Department of Physics Aksaray University

The structural, elastic, electronic, optical, and vibrational properties of cubic PdGa compound are investigated using the norm-conserving pseudopotentials within the local density approximation （LDA） in the framework of the density functional theory. The calculated lattice constant has been compared with the experimental value and has been found to be in good agreement with experimental data. The obtained electronic band structures show that PdGa compound has no band gap. The second-order elastic constants have been calculated, and the other related quantities such as the Young＇s modulus, shear modulus, Poisson＇s ratio, anisotropy factor, sound velocities, and Debye temperature have also been estimated. Our calculated results of elastic constants show that this compound is mechanically stable. Furthermore, the real and imaginary parts of the dielectric function and the optical constants such as the electron energy-loss function, the optical dielectric constant and the effective number of electrons per unit cell are calculated and presented in the study. The phonon dispersion curves are also derived using the direct method.

关键词： PdGa vibrational properties optical properties elastic constants

Predictions of pressure-induced structural transition,mechanical and thermodynamic properties of α-and β-Si_3N_4 ceramics:ab initio and quasi-harmonic Debye modeling

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2012年第6期21卷 130-140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 ab initio technique is used to investigate the structural and elastic properties of α-and β-Si3N4.The ground-state parameters accord quite well with the experimental data.Our calculation reveals that α-Si3N4 can retain its stability to at least 40 GPa when compressed at 300 K.The α → β phase transformation would not occur in a pressure range of 0-40 GPa and a temperature range of 0-300 K.Actually,the α → β transition occurs at 1600 K and 7.98 GPa.For α-and β-Si3N4,the c axes are slightly more incompressible than the a axes.We conclude that β-Si3N4 is a hard material and ductile in nature.On the other hand,β-Si3N4 is also found to be an ionic material and can retain its mechanical stability in a pressure range of 0-10 GPa.Besides,the thermodynamic properties such as entropy,heat capacity,and Debye temperature of α-and β-Si3N4 are determined at various temperatures and pressures.Significant features in these properties are observed at high temperature.The calculated results are in good agreement with available experimental data and previous theoretical values.Many fundamental solid-state properties are reported at high pressure and high temperature.Therefore,our results may provide useful information for theoretical and experimental investigations of the Si3N4 polymorphs.

关键词： ab initio elastic constants phase transition Poisson ratio

First-principles study of the structural,elastic,electronic,optical,and vibrational properties of intermetallic Pd_2Ga

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2012年第3期21卷 341-348页

作者： Yildirim A Koc H Deligoz E Department of Physics Siirt University Department of Physics Aksaray University

The structural, elastic, electronic, optical, and vibrational properties of the orthorhombic Pd2Ga compound are investigated using the norm-conserving pseudopotentials within the local density approximation in the frame of density functional theory. The calculated lattice parameters have been compared with the experimental values and found to be in good agreement with these results. The second-order elastic constants and the other relevant quantities, such as the Young＇s modulus, shear modulus, Poisson＇s ratio, anisotropy factor, sound velocity, and Debye temperature, have been calculated. It is shown that this compound is mechanically stable after analysing the calculated elastic constants. Furthermore, the real and imaginary parts of the dielectric function and the optical constants, such as the optical dielectric constant and the effective number of electrons per unit cell, are calculated and presented. The phonon dispersion curves are derived using the direct method. The present results demonstrate that this compound is dynamically stable.

关键词： Pd2Ga vibrational properties optical properties elastic constants

First-principles calculations on the elastic and thermodynamic properties of NbN

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2012年第12期21卷 420-429页

作者：任达华程新路 Institute of Atomic and Molecular Physics Sichuan University

The elastic and thermodynamic properties of NbN at high pressures and high temperatures are investigated by the plane-wave pseudopotential density functional theory （DFT）. The generalized gradient approximation （GGA） with the Perdew-Burke Ernzerhof （PBE） method is used to describe the exchange-correlation energy in the present work. The calculated equilibrium lattice constant a0, bulk modulus B0, and the pressure derivative of bulk modulus B~ of NbN with rocksalt structure are in good agreement with numerous experimental and theoretical data. The elastic properties over a range of pressures from 0 to 80.4 GPa are obtained. Isotropic wave velocities and anisotropic elasticity of NbN are studied in detail. It is indicated that NbN is highly anisotropic in both longitudinal and shear-wave velocities. According to the quasi-harmonic Debye model, in which the phononic effect is considered, the relations of （V - Vo）/Vo to the temperature and the pressure, and the relations of the heat capacity Cv and the thermal expansion coefficient α to temperature are discussed in a pressure range from 0 to 80.4 GPa and a temperature range from 0 to 2500 K. At low temperature, Cv is proportional to T3 and tends to the Dulong Petit limit at higher temperature. We predict that the thermal expansion coefficient α of NbN is about 4.20 × 10-6/K at 300 K and 0 GPa.

关键词： NbN density functional theory quasi-harmonic Debye model elastic constants thermo-dynamic properties

The effect of Co and Cr substitutions for Ni on mechanical properties and plastic deformation mechanism of FeMnCoCrNi high entropy alloys

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2020年第13期47卷 146-155页

作者： H.F.Zhang H.L.Yan H.Yu Z.W.Ji Q.M.Hu N.Jia Key Laboratory for Anisotropy and Texture of Materials(Ministry of Education) School of Material Science and EngineeringNortheastern UniversityShenyang 110819China State Key Lab Rolling&Automat Northeastern UniversityShenyang 110819China Institute of Metal Research Chinese Academy of ScienceShenyang 110016China Shen Yang University of Technology Shenyang 110870China Department of Materials Science and Engineering Southern University of Science and TechnologyShenzhen 518055China

The elastic constants,ideal tensile strength(ITS),stacking fault energy(SFE),lattice constant and magnetic moment of FeMnCoCrNi high entropy alloys with varying Co and Cr contents at 0 and 300 K were systematically investigated by first-principle calculations.For the alloys with Co substitution for Ni,at both temperatures the elastic stability of the face-centered cubic(fcc)phase,bulk elastic modulus(B),Young’s modulus(E),shear modulus(G)and ITS increase monotonically with increasing Co content.However,the Cauchy pressure(Cp),Pugh ratio(B/G),Poisson ratio(v),Zener anisotropy ratio(AZ)and elastic anisotropy ratio(AVR)decrease monotonically.The SFE also decreases with the increase of Co,resulting in the change of plastic deformation mechanism from dislocation slip to mechanical twinning,and then to hcp-martensitic transformation.This elucidates the underlying mechanism of the effect of Co addition on the strength and micromechanical behavior of FeMnCoCrNi alloys.Compared with Co,the Cr substitution for Ni leads to the more complex change of elastic constants and ITS.The increase of Cr shows the similar effect on SFE and deformation mechanism as that of Co.The variation of valence electron concentration and magnetism affect the SFE.The increase of either Co or Cr leads to the reduced magnetic moments of Fe and Mn.This could be responsible for the monotonic decrease of both lattice constant and SFE as the Co content increases.However,for the Cr addition case,multiple factors may affect the evolution of lattice constant and SFE.These findings shed light on the deformation mechanism of the alloys with different compositions.

关键词： High entropy alloys First-principle calculations elastic constants Ideal tensile strength Stacking fault energy

Effects of Mn Content on Mechanical Properties of FeCoCrNiMn_(x)(0≤x≤0.3)High-Entropy Alloys:A First-Principles Study

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2021年第4期34卷 455-464页

作者： Hui Xiao Yu Liu Kai Wang Zhipeng Wang Te Hu Touwen Fan Li Ma Pingying Tang School of Materials Science and Hydrogen Energy Foshan UniversityFoshan528001China School of Mechatronics Engineering Foshan UniversityFoshan528001China State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body Hunan UniversityChangsha410082China College of Materials Science and Engineering Hunan UniversityChangsha410082China Key Laboratory of New Electric Functional Materials of Guangxi Colleges and Universities Nanning Normal UniversityNanning530023China

Effects of Mn content on mechanical properties of FeCoCrNiMn_(x)(0≤x≤0.3)high-entropy alloys(HEAs)are investigated via first-prmciples calculations combining EMTO-CPA method.Related physical parameters,including lattice constant.elastic constants,elastic modulus,Pugh’s ratio,anisotropy factors,Poisson’s ratio,Cauchy pressure,Vickers hardness,yield strength,and energy factor,are calculated as a function of Mn content.The results show that the resistances to bulk,elastic,and shear deformation decrease with increasing Mn content.Pugh’s ratio B/G indicates that the ductility of FeCoCrNiMn_(x) HEAs has a remarkable reduction between 22 and 24% of Mn content.Meanwhile,Cauchy pressure suggests that the atomic bonding transforms from metallic to directional characteristic from 22 to 24% of Mn content.Vickers hardness and yield strength of FeCoCrNiMn HEA are intrinsically larger than those of FeCoCrNi HEA.Dislocation nucleation easily occurs in FeCoCrNiMn HE A compared to FeCoCrNi HEA,and large dislocation width in FeCoCrNiMnO_(2) HE A results in low stacking-fault energy,which easily induces twinning deformation.This work provides a valuable msieht for further theoretical and experimental study on the mechanical properties of FeCoCrNiMn_(x)(0≤x≤0.3)HEAs.

关键词： High-entropy alloys First-principles calculations Mechanical properties elastic constants Energy factor

First-principles calculations on elastic, magnetoelastic, and phonon properties of Ni_2FeGa magnetic shape memory alloys

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2018年第1期27卷 438-443页

作者：贺王强黄厚兵柳祝红马星桥 Department of Physics University of Science and Technology Beijing

The elastic, magnetoelastic, and phonon properties of Ni2FeGa were investigated through first-principles calculations. The obtained elastic and phonon dispersion curves for the austenite and martensite phases agree well with available the- oretical and experimental results. The isotropic elastic moduli are also predicted along with the polycrystalline aggregate properties including the bulk modulus, shear modulus, Young＇s modulus, and Poisson＇s ratio. The Pugh ratio indicates that Ni2FeGa shows ductility, especially the austenite phase, which is consistent with the experimental results. The Debye tem- peratures of the Ni2FeGa in the austenite and martensite phases are 344 K and 392 K, respectively. It is predicted that the magnetoelastic coefficient is -5.3 x 10^6 J/m3 and magnetostriction coefficient is between 135 and 55 ppm in the Ni2FeGa austenite phase.

关键词： Ni2FeGa elastic constants first-principles calculations magnetoelastic coefficients