The lattice parameters, elastic constants, cohesive energy, structural energy differences, as well as the properties of point defects and planar defects of hexagonal closepacked yttrium （hcpY） have been studied with...The lattice parameters, elastic constants, cohesive energy, structural energy differences, as well as the properties of point defects and planar defects of hexagonal closepacked yttrium （hcpY） have been studied with ab initio density functional theory for constructing an ex tensive database. Based on an analytical bondorder poial scheme, empirical manybody interatomic potential for hcpY has been developed. The model is fitted to some properties of Y, e.g., the lattice parameters, elastic constants, bulk modulus, cohesive energy, vacancy formation energy, and the structural energy differences. The present potential has ability to reproduce defect properties including the selfinterstitial atoms formation energies, vacancy formation energy, divacancy binding energy, as well as the bulk properties and the thermal dynamic properties.展开更多
The progressive stacking of chalcogenide single layers gives rise to two- dimensional semiconducting materials with tunable properties that can be exploited for new field-effect transistors and photonic devices. Yet t...The progressive stacking of chalcogenide single layers gives rise to two- dimensional semiconducting materials with tunable properties that can be exploited for new field-effect transistors and photonic devices. Yet the properties of some members of the chalcogenide family remain unexplored. Indium selenide （InSe） is attractive for applications due to its direct bandgap in the near infrared, controllable p- and n-type doping and high chemical stability. Here, we reveal the lattice dynamics, optical and electronic properties of atomically thin InSe flakes prepared by micromechanical cleavage. Raman active modes stiffen or soften in the flakes depending on which electronic bonds are excited. A progressive blue-shift of the photoluminescence peaks is observed for decreasing flake thickness （as large as 0.2 eV for three single layers）. First-principles calculations predict an even larger increase in the bandgap, 0.40 eV, for three single layers, and as much as 1.1 eV for a single layer. These results are promising from the point of view of the versatility of this material for optoelectronic applications at the nanometer scale and compatible with Si and III-V technologies.展开更多
The structural, electronic and lattice-dynamical properties of the intermetallic Al 2 Au at different electronic temperatures have been investigated via density functional calculations. The results of electronic densi...The structural, electronic and lattice-dynamical properties of the intermetallic Al 2 Au at different electronic temperatures have been investigated via density functional calculations. The results of electronic density of state indicate that, although its value changes considerably, Al2Au is still of metal with the increasing of electronic temperature. The acoustic mode of Al2Au gets negative which leads to lattice dynamical instability when the electronic temperature is beyond 1.44 eV. Moreover, with the increasing of the electronic temperature, the vibrational frequencies of the T1u optical mode (triply degenerate) of Al2Au at Γ point decrease first and increase then, the turning point is at Te = 1.40 eV. T2g optical mode at Γ point has a similar situation, but the turning point is at Te = 1.80 eV. The predicted melting temperatures of Al2Au undergo a sharp decrease from 1333K at normal temperature to 1172 K at Te = 1.8 eV after intense laser irradiation.展开更多
文摘The lattice parameters, elastic constants, cohesive energy, structural energy differences, as well as the properties of point defects and planar defects of hexagonal closepacked yttrium （hcpY） have been studied with ab initio density functional theory for constructing an ex tensive database. Based on an analytical bondorder poial scheme, empirical manybody interatomic potential for hcpY has been developed. The model is fitted to some properties of Y, e.g., the lattice parameters, elastic constants, bulk modulus, cohesive energy, vacancy formation energy, and the structural energy differences. The present potential has ability to reproduce defect properties including the selfinterstitial atoms formation energies, vacancy formation energy, divacancy binding energy, as well as the bulk properties and the thermal dynamic properties.
文摘The progressive stacking of chalcogenide single layers gives rise to two- dimensional semiconducting materials with tunable properties that can be exploited for new field-effect transistors and photonic devices. Yet the properties of some members of the chalcogenide family remain unexplored. Indium selenide （InSe） is attractive for applications due to its direct bandgap in the near infrared, controllable p- and n-type doping and high chemical stability. Here, we reveal the lattice dynamics, optical and electronic properties of atomically thin InSe flakes prepared by micromechanical cleavage. Raman active modes stiffen or soften in the flakes depending on which electronic bonds are excited. A progressive blue-shift of the photoluminescence peaks is observed for decreasing flake thickness （as large as 0.2 eV for three single layers）. First-principles calculations predict an even larger increase in the bandgap, 0.40 eV, for three single layers, and as much as 1.1 eV for a single layer. These results are promising from the point of view of the versatility of this material for optoelectronic applications at the nanometer scale and compatible with Si and III-V technologies.
文摘The structural, electronic and lattice-dynamical properties of the intermetallic Al 2 Au at different electronic temperatures have been investigated via density functional calculations. The results of electronic density of state indicate that, although its value changes considerably, Al2Au is still of metal with the increasing of electronic temperature. The acoustic mode of Al2Au gets negative which leads to lattice dynamical instability when the electronic temperature is beyond 1.44 eV. Moreover, with the increasing of the electronic temperature, the vibrational frequencies of the T1u optical mode (triply degenerate) of Al2Au at Γ point decrease first and increase then, the turning point is at Te = 1.40 eV. T2g optical mode at Γ point has a similar situation, but the turning point is at Te = 1.80 eV. The predicted melting temperatures of Al2Au undergo a sharp decrease from 1333K at normal temperature to 1172 K at Te = 1.8 eV after intense laser irradiation.
