Showing papers by "Hongming Weng published in 2009"

Revisiting magnetic coupling in transition-metal-benzene complexes with maximally localized Wannier functions

Abstract: Construction of maximally localized Wannier functions (MLWFs) has been implemented within the linear combination of pseudoatomic orbital method. Detailed analysis using MLWFs is applied to three closely related materials, single benzene (Bz) molecule, organometallic vanadium-Bz infinite chain, and ${\text{V}}_{2}{\text{Bz}}_{3}$ sandwich cluster. Two important results come out from the present analysis: (1) for the infinite chain, the validity of the basic assumption in the mechanism of Kanamori and Terakura for the ferromagnetic (FM) state stability is confirmed; (2) for ${\text{V}}_{2}{\text{Bz}}_{3}$, an important role played by the difference in the orbital energy between the edge Bzs and the middle Bz is revealed: the on-site energy of $p\ensuremath{\delta}$ states of edge Bzs is higher than that of middle Bz, which further reduces the FM stability of ${\text{V}}_{2}{\text{Bz}}_{3}$.

First-principles study of the rectifying properties of Pt / TiO 2 interface

Abstract: First-principles calculations have been performed to study the interface electronic structure of $\text{Pt}/{\text{TiO}}_{2}$ and to analyze the rectifying property of the $\text{Pt}/{\text{TiO}}_{2}/\text{Pt}$ structure. For the stoichiometric interface, the metal-induced gap states (MIGS) have amplitude appreciably only at the interface ${\text{TiO}}_{2}$. We will show that the presence of MIGS makes oxygen-vacancy formation energy small at the interface. It is therefore expected that the interfacial ${\text{TiO}}_{2}$ layer can be easily reduced. We will then demonstrate that the Schottky barrier height is strongly affected by oxygen deficiency. According to the present calculation, the interface is of Schottky-contact type for the fully oxidized interfacial ${\text{TiO}}_{2}$ while it becomes almost ohmic for strongly reduced one.