First-principles Study On Physical Properties O F Kagome-like Group-VA

Two dimensional materials are of most popularity in condensed physics in recent years,due to their novel electronic properties.The black phosphorene was prepared by mechanical methods in 2014.The blue phosphorene was predicted by first-principles calculations in 2014 and synthesized experimentally in 2016.Two years later,the black arsenene was fabricated on Si/SiO2 substrate.From then on,more and more two-dimensional materials of group-VA are discovered,which implies the importance for new allotrope structures of group-VA in the semiconductor optoelectronic devices.We predict a type of two dimensional materials with Kogome structure,whose crystal structure,electronic structure magnetism and transport properties are studied,in the current thesis.In the first part of our study,we performance a thorough structure search of P,As,Sb combined the Particle Swarm optimization based method CALYPSO and ab initio calculations,under the condition of normal pressure.The search results are compared with the experimental results,which acquires a Kagome-like structure called Kagome-VA with space group P3m1(164).In the following the electronic structure.magnetism and transport properties are studied.Kagome-P is a metastable phase of black phosphorus and blue phosphorus.Their kinetics,thermodynamics and mechanical stability can be shown by the phonon dispersion,molecular dynamics simulation and mechanical constants,separately.Results from the electronic structure calculations show that Kagome-P is an indirect band-gap semiconductor with 1.6 eV.The visible lights can be absorbed efficiently by Kagome-P.Usually,the direct band-gap semiconductors is much more efficient than the indirect ones for optoelectronic applications.Therefore,some efforts are made to induce transition from indirect to direct band-gap.At first,it is found that the transition can be achieved via strain engineering.The underlying mechanism of this transition is further revealed based on the bond nature of near-band-edge electronic orbitals.Secondly,the properties of kagome-p nanoribbons are investigated,based on the previous understanding that the H-absorption can also induce this transition.The corresponding electron transport properties and p-electron doping induced ferromagnetism are calculated,and the results indicate potential application for two-dimensional electronic devices.Finally,we performing a G-NEB simulation to confirm the Kagome-P can be obtained from P-trimers.Moreover,the phonon dispersion and the molecular dynamics simulation for Kagome-As and Kagome-Sb indicate their kinetic and thermodynamic stability,while the electronic structure shows an indirect band gap of about of 1.9 eV and 1.7eV,respectively.Similarly,the strain engineering is also effective for Kagome-As and Kagome-Sb.