The structural, electronic, optical and thermodynamic properties of Mo2Ga2C are investigated using density func- tional theory （DFT） within the generalized gradient approximation （GGA）. The optimized crystal struc...The structural, electronic, optical and thermodynamic properties of Mo2Ga2C are investigated using density func- tional theory （DFT） within the generalized gradient approximation （GGA）. The optimized crystal structure is obtained and the lattice parameters are compared with available experimental data. The electronic density of states （DOS） is calculated and analyzed. The metallic behavior for the compound is confirmed and the value of DOS at Fermi level is 4.2 states per unit cell per eV. Technologically important optical parameters （e.g., dielectric function, refractive index, absorption coefficient, photo conductivity, reflectivity, and loss function） are calculated for the first time. The study of dielectric constant （ε1） indicates the Drude-like behavior. The absorption and conductivity spectra suggest that the compound is metallic. The reflectance spectrum shows that this compound has the potential to be used as a solar reflector. The thermodynamic properties such as the temperature and pressure dependent bulk modulus, Debye temperature, specific heats, and thermal expansion coefficient of Mo2Ga2C MAX phase are derived from the quasi-harmonic Debye model with phononic effect also for the first time. Analysis of Tc expression using available parameter values （DOS, Debye temperature, atomic mass, etc.） suggests that the compound is less likely to be superconductor.展开更多
Crystal structure of Mg3Pd alloy was studied by first-principles calculations based on the density functional theory.The total energy,formation heat and cohesive energy of the two types of Mg3Pd were calculated to ass...Crystal structure of Mg3Pd alloy was studied by first-principles calculations based on the density functional theory.The total energy,formation heat and cohesive energy of the two types of Mg3Pd were calculated to assess the stability and the preferentiality.The results show that Mg3Pd alloy with Cu3P structure is more stable than Na3As structure,and Mg3Pd alloy is preferential to Cu3P structure.The obtained densities of states and charge density distribution for the two types of crystal structure were analyzed and discussed in combination with experimental findings for further discussion of the Mg3Pd structure.展开更多
There has been a long-standing debate on the European Union's democratic deficit. The issue was even more complicated today during the hard time of the European crises. However,a no-solution predicament inevitably...There has been a long-standing debate on the European Union's democratic deficit. The issue was even more complicated today during the hard time of the European crises. However,a no-solution predicament inevitably emerged under the traditional democratic deficit paradigm. This article proposed a new perspective regarding democracy and a new analysis framework to check the EU's institutional arrangement,under which the EU's democratic issue could be acceptably addressed.展开更多
文摘The structural, electronic, optical and thermodynamic properties of Mo2Ga2C are investigated using density func- tional theory （DFT） within the generalized gradient approximation （GGA）. The optimized crystal structure is obtained and the lattice parameters are compared with available experimental data. The electronic density of states （DOS） is calculated and analyzed. The metallic behavior for the compound is confirmed and the value of DOS at Fermi level is 4.2 states per unit cell per eV. Technologically important optical parameters （e.g., dielectric function, refractive index, absorption coefficient, photo conductivity, reflectivity, and loss function） are calculated for the first time. The study of dielectric constant （ε1） indicates the Drude-like behavior. The absorption and conductivity spectra suggest that the compound is metallic. The reflectance spectrum shows that this compound has the potential to be used as a solar reflector. The thermodynamic properties such as the temperature and pressure dependent bulk modulus, Debye temperature, specific heats, and thermal expansion coefficient of Mo2Ga2C MAX phase are derived from the quasi-harmonic Debye model with phononic effect also for the first time. Analysis of Tc expression using available parameter values （DOS, Debye temperature, atomic mass, etc.） suggests that the compound is less likely to be superconductor.
基金Project(07A070)supported by the Key Program of Educational Department of Hunan Province,ChinaProject(KF0504)supported by theOpen Project Program of the Key Laboratory of Low Dimensional Materials&Application Technology,Ministry of Education,China
文摘Crystal structure of Mg3Pd alloy was studied by first-principles calculations based on the density functional theory.The total energy,formation heat and cohesive energy of the two types of Mg3Pd were calculated to assess the stability and the preferentiality.The results show that Mg3Pd alloy with Cu3P structure is more stable than Na3As structure,and Mg3Pd alloy is preferential to Cu3P structure.The obtained densities of states and charge density distribution for the two types of crystal structure were analyzed and discussed in combination with experimental findings for further discussion of the Mg3Pd structure.
文摘There has been a long-standing debate on the European Union's democratic deficit. The issue was even more complicated today during the hard time of the European crises. However,a no-solution predicament inevitably emerged under the traditional democratic deficit paradigm. This article proposed a new perspective regarding democracy and a new analysis framework to check the EU's institutional arrangement,under which the EU's democratic issue could be acceptably addressed.
