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Density Functional Theory Investigation On The Magnetic And Conductive Properties Of Organic Molecule

Posted on:2005-04-16Degree:DoctorType:Dissertation
Country:ChinaCandidate:W D ZouFull Text:PDF
GTID:1101360152968953Subject:Materials Physics and Chemistry
Abstract/Summary:PDF Full Text Request
In this thesis, we adopt the density-functional theory (DFT) with generalized gradient approximation (GGA) to calculate the electronic band structure, the magnetic properties and the coexistence of magnetic and conductive properties of organic magnets by the accurate full potential linearized augmented plane wave (FP_LAPW) method. We have studied the electronic band structure and the ferromagnetic properties of pure organic magnets: NIT-2-O1 and 2-(5-pyrimidinyl)-4,4,5,5-tetramethyl-4,5-dihydro- H-3- oxoimidazol-1-oxylby using the first-principle method. We also have studied the electronic band structure and the ferromagnetic properties of non-pure organic magnets: TTTA·Cu(hfac)2 using this method. Finally, the ab initio calculation have been performed to study the coexistence of the magnetism and conductivity in Bis(ethylenediseleno) tetrathiafulvalene (BEST) with the Octahedral Anions Hexacyanoferrate(III) and Nitroprusside (BEST4[Fe(CN)6] and (BEST)2[Fe(CN)5NO])The results show that the spin magnetic moments of pure organic magnets which has stable nitroxide free radicals mainly assembled in nitroxide free radicals. The reason is that the unpaired electron in pure organic magnets is localized in the molecular orbital constituted primarily of the π*(NO) orbital, which is formed from 2p(π) atomic orbitals of N and O. The radical electrons are coupled by ferromagnetic interactions. The ab initio studies of the electronic structure and the magnetic properties of non-pure organic magnets: TTTA·Cu(hfac)2 revealed that the d electrons of transition metal and the unpaired electron of free radicals of ligand play an important role in the origin of magnetism, magnetic order structure and the net-work structure of non-pure organic magnets.We have investigated the conductive and the magnetic properties of the BEST4[Fe(CN)6] and (BEST)2[Fe(CN)5NO] by using ab initio method of the full potential linearized augmented-plane- wave with generalized gradient approximation (GGA). The results show that the magnetism and conductivity coexist in these materials. The contribution of the magnetic properties mainly lies in the [Fe(CN)6] and [Fe(CN)5NO] anions. The organic ligands bridge the magnetic center and form the complex magnetic structure. It is the charge transfer that induces the conductivity in these types compounds.
Keywords/Search Tags:organic magnet, first-principle, density-functional theory, FPLAPW, electronic band structure, density of state, coexistence of the magnetism and conductivity
PDF Full Text Request
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