Searching for two-dimensional（2 D） stable materials with direct band gap and high carrier mobility has attracted great attention for their electronic device applications.Using the first principles calculations and p...Searching for two-dimensional（2 D） stable materials with direct band gap and high carrier mobility has attracted great attention for their electronic device applications.Using the first principles calculations and particle swarm optimization（PSO） method,we predict a new 2 D stable material（HfNZ monolayer） with the global minimum of 2 D space.The HfNZ monolayer possesses direct band gap（～1.46 eV） and it is predicted to have high carrier mobilities(～103 cm2·V-1·s-1)from deformation potential theory.The direct band gap can be well maintained and flexibly modulated by applying an easily external strain under the strain conditions.In addition,the newly predicted HfN2 monolayer possesses good thermal,dynamical,and mechanical stabilities,which are verified by ab initio molecular dynamics simulations,phonon dispersion and elastic constants.These results demonstrate that HfN2 monolayer is a promising candidate in future microelectronic devices.展开更多
The structural, electronic, and elastic properties of cubic HC（NH2）2PbI3 perovskite are investigated by density functional theory using the Tkatchenko-Scheffler pairwise dispersion scheme. Our relaxed lattice parame...The structural, electronic, and elastic properties of cubic HC（NH2）2PbI3 perovskite are investigated by density functional theory using the Tkatchenko-Scheffler pairwise dispersion scheme. Our relaxed lattice parameters are in agreement with experimental data. The hydrogen bonding between NH2 and I ions is found to have a crucial role in FAPbI3 stability. The first calculated band structure shows that HC（NH2）2PbI3 has a direct bandgap （1.02 eV） at R-point, lower than the bandgap （1.53 eV） of CH3NH3PbI3. The calculated density of states reveals that the strong hybridization of s（Pb）-p（I） orbital in valence band maximum plays an important role in the structural stability. The photo-generated effective electron mass and hole mass at R-point along the R-Γ and R-M directions are estimated to be smaller：me^＊=0.06m0 and mh^＊=0.08m0 respectively, which are consistent with the values experimentally observed from long range photocarrier transport. The elastic properties are also investigated for the first time, which shows that HC（NH2）2PbI3 is mechanically stable and ductile and has weaker strength of the average chemical bond. This work sheds light on the understanding of applications of HC（NH2）2PbI3 as the perovskite in a planar-heterojunction solar cell light absorber fabricated on flexible polymer substrates.展开更多
We investigated the electronic and magnetic properties for O or Zn defect of (Cu, N) or (Cu, F)-co- doped ZnO with the concentration of 2.77% - 8.33% by using the first-principles calculations. The ferromagnetic coupl...We investigated the electronic and magnetic properties for O or Zn defect of (Cu, N) or (Cu, F)-co- doped ZnO with the concentration of 2.77% - 8.33% by using the first-principles calculations. The ferromagnetic coupling of Cu atoms in (Cu, N)-codoped ZnO can be attributed to the hole-mediated double-exchange through the strong 2p-3d coupling between Cu and neighboring O (or N) atoms. The ferromagnetism in Cu-doped ZnO is controllable by changing the carrier density. The Cu magnetic moment in low Cu concentration (2.77%) is increased by the N-doping, while for the F-doping it decreases. For two Cu atoms of Zn0.9445Cu0.0555O with O vacancy, the antiferromagnetic state is more energetically favorable than the ferromagnetic state.展开更多
基金Project supported by the National Natural Science Foundation(Grant No.U1404108)the Innovative Talents of Universities in Henan Province of China(Grant No.17HASTIT013)+1 种基金the Basic and Frontier Technology Research Program of Henan Province of China(Grant No.162300410056)the Key Scientific Research Projects of Higher Institutions in Henan Province of China(Grant No.19A140018).
文摘Searching for two-dimensional（2 D） stable materials with direct band gap and high carrier mobility has attracted great attention for their electronic device applications.Using the first principles calculations and particle swarm optimization（PSO） method,we predict a new 2 D stable material（HfNZ monolayer） with the global minimum of 2 D space.The HfNZ monolayer possesses direct band gap（～1.46 eV） and it is predicted to have high carrier mobilities(～103 cm2·V-1·s-1)from deformation potential theory.The direct band gap can be well maintained and flexibly modulated by applying an easily external strain under the strain conditions.In addition,the newly predicted HfN2 monolayer possesses good thermal,dynamical,and mechanical stabilities,which are verified by ab initio molecular dynamics simulations,phonon dispersion and elastic constants.These results demonstrate that HfN2 monolayer is a promising candidate in future microelectronic devices.
基金supported by the National Natural Science Foundation of China(Grant No.51572219)the Natural Science Foundation of Shaanxi Province,China(Grant No.2015JM1018)+3 种基金the Graduate Innovation Fund of Northwest University of China(Grant No.YJG15007)the Henan Provincial Foundation and Frontier Technology Research Program,China(Grant Nos.2013JCYJ12 and 2013JCYJ13)the Fund from Henan University of Technology,China(Grant No.2014YWQN08)the Natural Science Fund from the Henan Provincial Education Department,China(Grant No.16A140027)
文摘The structural, electronic, and elastic properties of cubic HC（NH2）2PbI3 perovskite are investigated by density functional theory using the Tkatchenko-Scheffler pairwise dispersion scheme. Our relaxed lattice parameters are in agreement with experimental data. The hydrogen bonding between NH2 and I ions is found to have a crucial role in FAPbI3 stability. The first calculated band structure shows that HC（NH2）2PbI3 has a direct bandgap （1.02 eV） at R-point, lower than the bandgap （1.53 eV） of CH3NH3PbI3. The calculated density of states reveals that the strong hybridization of s（Pb）-p（I） orbital in valence band maximum plays an important role in the structural stability. The photo-generated effective electron mass and hole mass at R-point along the R-Γ and R-M directions are estimated to be smaller：me^＊=0.06m0 and mh^＊=0.08m0 respectively, which are consistent with the values experimentally observed from long range photocarrier transport. The elastic properties are also investigated for the first time, which shows that HC（NH2）2PbI3 is mechanically stable and ductile and has weaker strength of the average chemical bond. This work sheds light on the understanding of applications of HC（NH2）2PbI3 as the perovskite in a planar-heterojunction solar cell light absorber fabricated on flexible polymer substrates.
文摘We investigated the electronic and magnetic properties for O or Zn defect of (Cu, N) or (Cu, F)-co- doped ZnO with the concentration of 2.77% - 8.33% by using the first-principles calculations. The ferromagnetic coupling of Cu atoms in (Cu, N)-codoped ZnO can be attributed to the hole-mediated double-exchange through the strong 2p-3d coupling between Cu and neighboring O (or N) atoms. The ferromagnetism in Cu-doped ZnO is controllable by changing the carrier density. The Cu magnetic moment in low Cu concentration (2.77%) is increased by the N-doping, while for the F-doping it decreases. For two Cu atoms of Zn0.9445Cu0.0555O with O vacancy, the antiferromagnetic state is more energetically favorable than the ferromagnetic state.
