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
Applying calculation method in alloy design should be an important tendency due to its characters of inexpensive cost, high efficiency and prediction. DOS calculations of AuSn, AsSn and SbSn Sn- based alloys have ...Applying calculation method in alloy design should be an important tendency due to its characters of inexpensive cost, high efficiency and prediction. DOS calculations of AuSn, AsSn and SbSn Sn- based alloys have been investigated by employing DV - Xa method, in which different cluster models were adopted to calculate electron structure.It is proved that some regulations must be taken into ac- count in order to carry out alloy design calculation successfully,which are described in this paper in detail.展开更多
The preparation, characterization, and test of the first wall materials designed to be used in the fusion reactor have remained challenging problems in the material science. This work uses the firstprinciples method a...The preparation, characterization, and test of the first wall materials designed to be used in the fusion reactor have remained challenging problems in the material science. This work uses the firstprinciples method as implemented in the CASTEP package to study the influ ences of the doped titanium carbide on the structural sta bility of the WTiC material. The calculated total energy and enthalpy have been used as criteria to judge the structural models built with consideration of symmetry. Our simulation indicates that the doped TiC tends to form its own domain up to the investigated nanoscale, which implies a possible phase separation. This result reveals the intrinsic reason for the composite nature of the WTiC material and provides an explanation for the experimen tally observed phase separation at the nanoscale. Our approach also sheds a light on explaining the enhancing effects of doped components on the durability, reliability, corrosion resistance, etc., in many special steels.展开更多
一、重点单词1.spread【考纲释义】vt.& vi.传播;伸展;展开【备考实例】Papermaking began in China and from here it ____ to North Africa and Europe. A.grew B.carried C.spread D.developed【考点解析】句意"
1.What do you have in mind?(P72)【考点】have sth.in mind【归纳】have sth.in mind:想到某事;想要做某事;have sb.in mind心中想着某人【高考链接】(1)Fred,who had expected how it would go with his daughter,had a great worry ...1.What do you have in mind?(P72)【考点】have sth.in mind【归纳】have sth.in mind:想到某事;想要做某事;have sb.in mind心中想着某人【高考链接】(1)Fred,who had expected how it would go with his daughter,had a great worry _____his mind.(06湖南) A.on B.in C.with D.at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Applying calculation method in alloy design should be an important tendency due to its characters of inexpensive cost, high efficiency and prediction. DOS calculations of AuSn, AsSn and SbSn Sn- based alloys have been investigated by employing DV - Xa method, in which different cluster models were adopted to calculate electron structure.It is proved that some regulations must be taken into ac- count in order to carry out alloy design calculation successfully,which are described in this paper in detail.
基金finantially supported by the Science Foundation for International Cooperation of Sichuan Province (2014HH0016)the Fundamental Research Funds for the Central Universities (SWJTU2014: A0920502051113-10000)National Magnetic Confinement Fusion Science Program (2011GB112001)
文摘The preparation, characterization, and test of the first wall materials designed to be used in the fusion reactor have remained challenging problems in the material science. This work uses the firstprinciples method as implemented in the CASTEP package to study the influ ences of the doped titanium carbide on the structural sta bility of the WTiC material. The calculated total energy and enthalpy have been used as criteria to judge the structural models built with consideration of symmetry. Our simulation indicates that the doped TiC tends to form its own domain up to the investigated nanoscale, which implies a possible phase separation. This result reveals the intrinsic reason for the composite nature of the WTiC material and provides an explanation for the experimen tally observed phase separation at the nanoscale. Our approach also sheds a light on explaining the enhancing effects of doped components on the durability, reliability, corrosion resistance, etc., in many special steels.
文摘一、重点单词1.spread【考纲释义】vt.& vi.传播;伸展;展开【备考实例】Papermaking began in China and from here it ____ to North Africa and Europe. A.grew B.carried C.spread D.developed【考点解析】句意"
文摘1.What do you have in mind?(P72)【考点】have sth.in mind【归纳】have sth.in mind:想到某事;想要做某事;have sb.in mind心中想着某人【高考链接】(1)Fred,who had expected how it would go with his daughter,had a great worry _____his mind.(06湖南) A.on B.in C.with D.at
