蔬菜采种中的层性原理及应用

蔬菜作物种子的生理异质性,除受其遗传特性决定之外,还与该作物株型所特有的结构及种子(或果实)在种株上的着生部位有直接关系。即种子的质量和产量因种株的分枝习性及种子(或果实)在花序(或种株)上的着生部位不同而表现出差异,这就是“

First-principles study of stacking fault energies in Ni_3Al intermetallic alloys

The first-principles method based on the projector augmented wave method within the generalized gradient approximation was employed to calculate the superlattice intrinsic stacking fault（SISF） and complex stacking fault（CSF） energies of the binary Ni3Al alloys with different Al contents and the ternary Ni3Al intermetallic alloys with addition of alloying elements,such as Pd,Pt,Ti,Mo,Ta,W and Re.The results show that the energies of SISF and CSF increase significantly with increase of Al contents in Ni3Al.Addition of Pd and Pt occupying the Ni sublattices does not change the SISF and CSF energies of Ni3Al markedly in comparison with the Ni-23.75Al alloy.While addition of alloying elements,such as Ti,Mo,Ta,W and Re,occupying the Al sublattices dramatically increases the SISF and CSF energies of Ni3Al.The results suggest that the energies of SISF and CSF are dependent both on the Al contents and on the site occupancy of the ternary alloying element in Ni3Al intermetallic alloys.

First-Principles Study of Lithium and Sodium Atoms Intercalation in Fluorinated Graphite

The structure evolution of fluorinated graphite （CFx） upon the Li/Na intercalation has been studied by first- principles calculations. The Li/Na adsorption on single CF layer and intercalated into bulk CF have been calculated. The better cycling performance of Na intercalation into the CF cathode, comparing to that of Li intercalation, is attributed to the different strength and characteristics of the Li-F and Na-F interactions. The interactions between Li and F are stronger and more localized than those between Na and E The strong and localized Coulomb attraction between Li and F atoms breaks the C-F bonds and pulls the F atoms away, and graphene sheets are formed upon Li intercalation.

Threshold voltage modulation in monolayer MoS_(2) field-effect transistors via selective gallium ion beam irradiation

Electronic regulation of two-dimensional(2 D)transition metal dichalcogenides(TMDCs)is a crucial step towards next-generation optoelectronics and electronics.Here,we demonstrate controllable and selective-area defect engineering in 2D molybdenum disulfide(MoS_(2))using a focused ion beam with a low-energy gallium ion(Ga^(+))source.We find that the surface defects of MoS_(2)can be tuned by the precise control of ion energy and dose.Furthermore,the fieldeffect transistors based on the monolayer MoS_(2)show a significant threshold voltage modulation over 70 V after Ga+irradiation.First-principles calculations reveal that the Ga impurities in the monolayer MoS_(2)introduce a defect state near the Fermi level,leading to a shallow acceptor level of 0.25 eV above the valence band maximum.This defect engineering strategy enables direct writing of complex pattern at the atomic length scale in a controlled and facile manner,tailoring the electronic properties of 2D TMDCs for novel devices.

First-principles study of lithium intercalated bilayer graphene

Litbium intercalated bilayer graphene has been investigated using first-principles density functional theory calculations. Re- sults show that there exist AB and AA stacking sequences for bilayer graphene in which the latter is more favorable for the Li storage and the former will evolve into the latter with the intercalation of Li ions. The relationship between the interlayer dis- tance of two graphene sheets and the intercalated capacity of Li ions is discussed, It is found that structural defect is identified to store Li ions more favorably than pristine bilayer graphene and an isolated C atom vacancy in bilayer graphene can capture three Li ions between two graphene sheets.