The effect of pressure on structural, mechanical properties as well as the temperature dependence of thermodynamic properties of TiAl alloy are investigated by implementing first-principles calculations. The results s...The effect of pressure on structural, mechanical properties as well as the temperature dependence of thermodynamic properties of TiAl alloy are investigated by implementing first-principles calculations. The results show that the volume decrea-ses with the pressure increasing. We calculated the CtJ at various pressures and all the results satisfy mechanical stability crite-ria, thus the TiAl alloy is mechanically stable. The elastic constants？ bulk modulus and shear modulus calculated are well in a-greement with the calculated values at zero the pressure. The bulk modulus and shear modulus increase with the pressure in-creasing, which reflects the deformation resistance, and accordingly, deformation resistance can be strengthened with the in-crease of pressure. The brittle nature of TiAl alloy turns to ductile nature in 10 - 20 GPa . The Debye temperature, linear ther-mal expansion and heat capacity are calculated using the quasi-harmonic Debye model under the pressure ranging from 0 to 50 GPa and the temperature ranging from 0 to 1 000 K, which are useful to investigate the effect of temperature and pressure on thermodynamic parameters. Finally, electronic structure is calculated at various pressures,and it can be found that the peak intensity decreases with increasing pressure and the the strength of d-d orbital of Ti is weakened but the ductility is enhanced.展开更多
NaxCoO2 is a commonly used cathode material for sodium ion batteries because of its easy synthesis, high reversible capacity and good cyclability. The structural and electrochemical properties of NaxCoO2 during sodium...NaxCoO2 is a commonly used cathode material for sodium ion batteries because of its easy synthesis, high reversible capacity and good cyclability. The structural and electrochemical properties of NaxCoO2 during sodium ion insertion/extraction process are studied based on first principles calculations. The calculation results of crystal structure parameters and average intercalation voltage are in good agreement with experiment data. Through calculation of the geometric structure and charge transfer in charging and discharging processes of NaxCoO2, it is found that the oxygen atom surrounding Co of the CoO6 octahedral screens the coulomb potential produced by sodium vacancy in NaxCoO2, and the charge is removed from the entire Co-O layer instead of the Co atom adjacent to sodium vacancy when sodium ions are extracted from the Na CoO2 lattice. Thus, during the insertion/extraction of sodium ion from Na CoO2, the CoO6 octahedral structure undergoes small lattice distortion, which makes the local structure quite stable and is beneficial to the cycling stability of the material for the application of sodium ion batteries.展开更多
The atomic and electronic structures of amorphous CuxZr100-x(x=36,46,50,56,64) alloys were simulated using first-principle calculations within a 400-atom supercell.The pair correlation function,coordination numbers,lo...The atomic and electronic structures of amorphous CuxZr100-x(x=36,46,50,56,64) alloys were simulated using first-principle calculations within a 400-atom supercell.The pair correlation function,coordination numbers,local cluster structures and electronic density of states were analyzed.Reasonable agreements between the theory and the experiments were obtained.The amorphous alloys exhibit different local cluster structures and can all be explained with cluster formulas [cluster](glue)1,3,where the clusters are derived from known Cu-Zr compounds.There is always a pseudogap in the density of state at the Fermi level.展开更多
基金National Natural Science Foundation of China(Nos.U1610123,51674226,51574207,51574206,51274175)International Cooperation Project of the Ministry of Science and Technology of China(No.2014DFA50320)+3 种基金Science and Technology Major Project of Shanxi Province(No.MC2016-06)International Science and Technology Cooperation Project of Shanxi Province(No.2015081041)Research Project Supported by Shanxi Scholarship Council of China(No.2016-Key 2)Transformation of Scientific and Technological Achievements Special Guide Project of Shanxi Province(No.201604D131029)
文摘The effect of pressure on structural, mechanical properties as well as the temperature dependence of thermodynamic properties of TiAl alloy are investigated by implementing first-principles calculations. The results show that the volume decrea-ses with the pressure increasing. We calculated the CtJ at various pressures and all the results satisfy mechanical stability crite-ria, thus the TiAl alloy is mechanically stable. The elastic constants？ bulk modulus and shear modulus calculated are well in a-greement with the calculated values at zero the pressure. The bulk modulus and shear modulus increase with the pressure in-creasing, which reflects the deformation resistance, and accordingly, deformation resistance can be strengthened with the in-crease of pressure. The brittle nature of TiAl alloy turns to ductile nature in 10 - 20 GPa . The Debye temperature, linear ther-mal expansion and heat capacity are calculated using the quasi-harmonic Debye model under the pressure ranging from 0 to 50 GPa and the temperature ranging from 0 to 1 000 K, which are useful to investigate the effect of temperature and pressure on thermodynamic parameters. Finally, electronic structure is calculated at various pressures,and it can be found that the peak intensity decreases with increasing pressure and the the strength of d-d orbital of Ti is weakened but the ductility is enhanced.
基金Project(51472211)supported by the National Natural Science Foundation of ChinaProject(2012CK1006)supported by Scientific and Technical Achievement Transformation Fund of Hunan Province,China
文摘NaxCoO2 is a commonly used cathode material for sodium ion batteries because of its easy synthesis, high reversible capacity and good cyclability. The structural and electrochemical properties of NaxCoO2 during sodium ion insertion/extraction process are studied based on first principles calculations. The calculation results of crystal structure parameters and average intercalation voltage are in good agreement with experiment data. Through calculation of the geometric structure and charge transfer in charging and discharging processes of NaxCoO2, it is found that the oxygen atom surrounding Co of the CoO6 octahedral screens the coulomb potential produced by sodium vacancy in NaxCoO2, and the charge is removed from the entire Co-O layer instead of the Co atom adjacent to sodium vacancy when sodium ions are extracted from the Na CoO2 lattice. Thus, during the insertion/extraction of sodium ion from Na CoO2, the CoO6 octahedral structure undergoes small lattice distortion, which makes the local structure quite stable and is beneficial to the cycling stability of the material for the application of sodium ion batteries.
基金supported by the National Basic Research Program of China (Grant No 2007CB613902)the National Natural Science Foundation of China (Grant Nos 50901012 and 50631010)
文摘The atomic and electronic structures of amorphous CuxZr100-x(x=36,46,50,56,64) alloys were simulated using first-principle calculations within a 400-atom supercell.The pair correlation function,coordination numbers,local cluster structures and electronic density of states were analyzed.Reasonable agreements between the theory and the experiments were obtained.The amorphous alloys exhibit different local cluster structures and can all be explained with cluster formulas [cluster](glue)1,3,where the clusters are derived from known Cu-Zr compounds.There is always a pseudogap in the density of state at the Fermi level.
