First-principles Study Of Transport And Adsorption Properties Of Metal-phthalocyanines

With the rapid progress of theory and its numerical methods, the density functionaltheory (DFT) based first-principles calculation has become a routine method used incondensed matter physics, quantum chemistry, material science, molecular electronicsand surface science and so on. DFT calculations can be not only used to explain theexperimental observations and to reveal the underlying physics, but also can be usedto give some theoretical predictions. The dissertation for Master degree of Scienceincludes the following three chapters.In chapter 1, we firstly concisely introduce the latest progress of surface adsorp-tion and the current status of metal-phthalocyanine research. Then we introduce thetheoretical methods and some simulation packages used in this dissertation. In ourcalculations, the first-principles calculations are used to optimize the geometric struc-tures and calculation the electronic structures. While the nonequlibrium Gree's functiontechnique combined with DFT calculations are used to explore the transport propertiesof several junctions.In chapter two,we focus on the transport properties through MPc junctions con-structed by sandwiching the MPc molecules between two semi-infinite graphene nanorib-bons. Our calculations are realized by employing the nonequilibrium Green's functiontechnique combined with DFT calculations. Theoretical results indicate that the trans-port properties of MPc molecules can be effectively tuned by changing of the centralmetal atoms. Moreover, according to the calculated spin-resolved transmission spectra,we find that MnPc and FePc can be used to design almost perfect spin-filters.In the third chapter, we turn to characterize the adsorption behavior of SnPc moleculeon Ag(111) surface with Sn-up and Sn-down conformations. Two optimized geometricstructures are very close to the determined geometries in experiments. SnPc moleculeenergetically prefers to adsorb on Ag(111) surface with Sn-down conformation. Thesimulated scanning tunneling microscopy images reproduce the main features of ex-perimental observations. The energy required to move the central Sn atom through theframe of a phthalocyanine molecule, switching from the Sn-up to Sn-down conforma-tion, is about 1.68 eV. Moreover, the experimentally proposed hole attached mechanismis verified based on the calculated density of states of SnPc on Ag(111) with differentadsorption configurations.