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Theoretical Studies On The Function Of Low-Dimensional Nano Materials In The Design Of Novel Function Materials

Posted on:2019-08-25Degree:MasterType:Thesis
Country:ChinaCandidate:B SuFull Text:PDF
GTID:2481306470499684Subject:Chemical Engineering and Technology
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With the studies of new nano-materials and the rise of various modern research techniques,the development and application of nano-functional materials have been greatly promoted.In the present article,two novel nano-functional materials,one dimensional nitrogen-riched complex and two dimensional spin magnetic material,are respectively constructed by using the methods of encapsulation in one dimensional nanotube and doping in two dimensional nano sheet.The roles of the low dimensional nanomaterials in the design of high-energy nitrogen-riched materials and magnetic semiconductor materials are studied by using the density functional theory.The main research contents and results are listed as follows:(1)Two theoretical calculation models are used to study the confinement effect of BN nanocube(BNNT)in stabilizing the neutral pentagon N5 ring,inside a finite-sized tube of BNNT for molecular calculations and an infinite 1D BNNT for periodic calculations.The novel nanoscale high energy material model complex molecule N5@M-BNNT of the N5ring in a model BNNT(M-BNNT)is calculated at the B3LYP-D3/6-311G(dp)and?B97X-D/6-311G(d,p)levels of theory.The results indicate that the confined environment of M-BNNT could stabilize the N5 ring,due to the electrostatic interaction induced by the charge transfers of 0.85 e from M-BNNT to N5.Then,the ab initio electronic structure calculations confirm the stability of the one-dimensional N5@1D-BNNT system of the more N5 rings encapsulated inside the one-dimensional BNNT(1D-BNNT)and the similar charge transfer of 0.89 e from 1D-BNNT to the N5 ring.At last,the ab initio molecular dynamics calculation demonstrates the stability of N5@1D-BNNT at room temperature.Therefore,it could be expected that BNNT could provide a well confined environment to encapsulate polynitrogen clusters as well as the N5@BNNT is an active ingredient of the promising high-energy nano structural materials and a good candidate for experimental preparation in future.(2)The structural and magnetic properties of 5d series transition metal atom substitutionally doped blue phosphorene are systematically investigated.The spin polarized state can be induced in the doped blue phosphorene,except for the Ir and Pt-doped systems.Spin density and Bader charge analyses indicate that the magnetic moments of the5d-doped systems mainly originate from the 5d electrons of the TMs,except for the Au and Hg-doped systems whose magnetism aremainly attribute to the neighboring P atoms.The electronic structure calculations indicate that the Ir and Pt-doped systems show semiconducting and metallic behaviors,respectively.The W and Os-doped systems show dilute magnetic semiconductor properties and the Au-doped system shows metallic behavior.Especially,the Hf,Ta,Re and Hg-doped system exhibits half-metallic state.Moreover,the Re-doped system shows the largest magnetocrystalline anisotropy energy(MAE)of-30.25 me V in the present studied systems,showing the most stable magnetism,and its MAE could be enhanced to-42.97 me V by applying an electronic field.Our study demonstrates that the 5d doping could provide various potential applications in spintronics and magnetic storage devices for blue phosphorene.(3)The structure,energy,electron and magnetic property of lanthanide doped blue phosphorene are systematically investigated by using GGA+U method.From La to Gd-doped blue phosphorene,the calculated spin magnetic moments are respectively 0.0,1.0,2.0,3.0,4.0,8.0 and 7.0?B.The spin charge density and Bader charge analysis indicate that the magnetic moments of the lanthanide atom doped systems are mainly come from the lanthanide atoms.Specifically,Pr-doped system has a MAE of up to 66.68 me V with the easy magnetization axis parallel to the blue-phosphorus plane,and the MAE could be enhanced to 103.51 me V by applying an electronic field.The electronic structure calculations show that the La-doped blue phosphor is nonmagnetic and retains its semiconductor characteristic.However,other doped systems exhibit spin polarization states and have different electronic structure properties.The Pr,Nd,Pm and Gd-doped blue phosphorene have the dilute magnetic semiconductor properties,whereas the Ce and Eu-doped blue phosphorene exhibit the half-metallic behavior.The calculated results show that the semi-metallic or dilute magnetic semiconductor characteristics can be achieved by the substitution of lanthanide metal atoms for blue phosphorene.Therefore,lanthanide-doped blue phosphorene is expected to become a novel dilute magnetic semiconductor material,which has potential applications in spintronics and magnetic storage devices.
Keywords/Search Tags:nano functional material, nitrogen-riched material, encapsulation, magnetic semiconductor materials, doping, density functional theory calculation
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