Yuanping Sun

Dielectric properties of a-axis-oriented orthorhombic HoMnO3 thin films

Orthorhombic HoMnO3 films were prepared epitaxially on Nb-doped SrTiO3 (110) single crystal substrates by using pulsed laser deposition technique. The films showed perfectly a-axis crystallographic orientations and were well aligned with the substrates. The complex dielectric properties of HoMnO3 films were measured as functions of temperature (77–250 K) and frequency (100 Hz–100 kHz). Thermally activated dielectric relaxations were found, and the respective peaks shifted to higher temperatures as the measuring frequency increased. The frequency dependence of dielectric properties was ascribed to the universal dielectric response models, and the hopping conductivity and the dipolar effects induced by the charge carriers were used to explain the results.

A DFT STUDY ON THE ELECTRONIC CHARACTER OF P700

This density functional study is devoted to the long debated electronic nature of P700+. We found that P700+ is intrinsically a dimer of chlorophyll molecules. The unpaired electron spin distributes equally over two chlorophyll molecule halves in the bare P700+, while the dressed P700+ shows the spin density asymmetry mainly coming from the H-bond donated to 131-keto-O of one half. The experimental contradictions on the electronic nature of P700+ are also discussed.