The electronic structure of GaAs/Al xGa 1-x As superlattices has been investigated by an ab initio calculation method—the conjugate gradient (CG) approach.In order to determine that,a conventional CG scheme is m...The electronic structure of GaAs/Al xGa 1-x As superlattices has been investigated by an ab initio calculation method—the conjugate gradient (CG) approach.In order to determine that,a conventional CG scheme is modified for our superlattices:First,apart from the former scheme,for the fixed electron density n(z),the eigenvalues and eigenfunctions are calculated,and then by using those,reconstruct the new n(z).Also,for every k z,we apply the CG schemes independently.The calculated energy difference between two minibands,and Fermi energy are in good agreement with the experimental data.展开更多
The electronic structure of GaAs/Al xGa 1-x As superlattices has been investigated by an ab initio calculation method—the conjugate gradient (CG) approach.In order to determine that,a conventional CG scheme is m...The electronic structure of GaAs/Al xGa 1-x As superlattices has been investigated by an ab initio calculation method—the conjugate gradient (CG) approach.In order to determine that,a conventional CG scheme is modified for our superlattices:First,apart from the former scheme,for the fixed electron density n(z),the eigenvalues and eigenfunctions are calculated,and then by using those,reconstruct the new n(z).Also,for every k z,we apply the CG schemes independently.The calculated energy difference between two minibands,and Fermi energy are in good agreement with the experimental data.展开更多
The structural and thermodynamic properties of TiAI intermetallics under high pressure have been investigated by ab initio plane-wave pseudopotential density functional theory method. It is found that the ratio of lat...The structural and thermodynamic properties of TiAI intermetallics under high pressure have been investigated by ab initio plane-wave pseudopotential density functional theory method. It is found that the ratio of lattice parameter c to a keeps almost constant with a value of 1.02 under the pressure from 0 to 20 GPa, which agrees well with the experimental results. With the pressure increasing from 20 to 45 GPa the values of c/a decrease almost linearly from 1.02 to 0.99. These calculated results indicate under low pressure the variation rate for a-axis is almost the same to that for c-axis, but under higher pressure the variation for a-axis is smaller than along e-axis. Through the quasi-harmonic Debye model, the equation of state （EOS） of TiAI intermetallies, as well as the thermal expansion and heat capacity at various pressures and temperatures are also studied.展开更多
Al-1.1%Sc and A1-2%Sc （mass fraction） alloys were prepared using gas atomized alloy particles. Samples from consolidated alloys were analyzed by XRD for the determination of lattice parameters. Using these lattice p...Al-1.1%Sc and A1-2%Sc （mass fraction） alloys were prepared using gas atomized alloy particles. Samples from consolidated alloys were analyzed by XRD for the determination of lattice parameters. Using these lattice parameters, the mechanical properties of the alloys were calculated theoretically with WIEN2k and EMTO programs, respectively. The elasticity moduli of the experimentally produced alloys were compared with the theoretical calculation results. The calculated mechanical properties of A13Sc phase and A1-Sc alloys were discussed to determine the optimum Sc content of Al-Sc alloys. It may be concluded that the Sc content should be the maximum about 1.0%, much more Sc addition could not improve the mechanical properties of the alloys.展开更多
基金Supported by National Natural Science Foundation of China(No.50 0 72 0 1 5 and No.5980 1 0 0 6) and Tianjin Youth Foundation o
文摘The electronic structure of GaAs/Al xGa 1-x As superlattices has been investigated by an ab initio calculation method—the conjugate gradient (CG) approach.In order to determine that,a conventional CG scheme is modified for our superlattices:First,apart from the former scheme,for the fixed electron density n(z),the eigenvalues and eigenfunctions are calculated,and then by using those,reconstruct the new n(z).Also,for every k z,we apply the CG schemes independently.The calculated energy difference between two minibands,and Fermi energy are in good agreement with the experimental data.
基金Supported by National Natural Science Foundation of China(No.50 0 72 0 1 5 and No.5980 1 0 0 6) and Tianjin Youth Foundation o
文摘The electronic structure of GaAs/Al xGa 1-x As superlattices has been investigated by an ab initio calculation method—the conjugate gradient (CG) approach.In order to determine that,a conventional CG scheme is modified for our superlattices:First,apart from the former scheme,for the fixed electron density n(z),the eigenvalues and eigenfunctions are calculated,and then by using those,reconstruct the new n(z).Also,for every k z,we apply the CG schemes independently.The calculated energy difference between two minibands,and Fermi energy are in good agreement with the experimental data.
基金Support from Ph. D. Program Foundation (B2009-59)the National Science Foundations of China under Grant No. 50802024+1 种基金Henan Educational Committee under Grant No. 2011A140007Young Key Teacher by Henan Polytechnic University
文摘The structural and thermodynamic properties of TiAI intermetallics under high pressure have been investigated by ab initio plane-wave pseudopotential density functional theory method. It is found that the ratio of lattice parameter c to a keeps almost constant with a value of 1.02 under the pressure from 0 to 20 GPa, which agrees well with the experimental results. With the pressure increasing from 20 to 45 GPa the values of c/a decrease almost linearly from 1.02 to 0.99. These calculated results indicate under low pressure the variation rate for a-axis is almost the same to that for c-axis, but under higher pressure the variation for a-axis is smaller than along e-axis. Through the quasi-harmonic Debye model, the equation of state （EOS） of TiAI intermetallies, as well as the thermal expansion and heat capacity at various pressures and temperatures are also studied.
文摘Al-1.1%Sc and A1-2%Sc （mass fraction） alloys were prepared using gas atomized alloy particles. Samples from consolidated alloys were analyzed by XRD for the determination of lattice parameters. Using these lattice parameters, the mechanical properties of the alloys were calculated theoretically with WIEN2k and EMTO programs, respectively. The elasticity moduli of the experimentally produced alloys were compared with the theoretical calculation results. The calculated mechanical properties of A13Sc phase and A1-Sc alloys were discussed to determine the optimum Sc content of Al-Sc alloys. It may be concluded that the Sc content should be the maximum about 1.0%, much more Sc addition could not improve the mechanical properties of the alloys.
