Communication: The reason why +c ZnO surface is less stable than -c ZnO surface: first-principles calculation

It has been experimentally shown that an O(-c)-polar ZnO surface is more stable than a Zn(+c)-polar surface in H(2) ambient. We applied first-principles calculations to investigating the polarity dependence on the stability at the electronic level. The calculations revealed that the -c surface terminated with H atom was stable maintaining a wurtzite structure, whereas the +c surface was unstable due to the change of coordination numbers of Zn at the topmost surface from four (wurtzite) to six (rock salt). This causes the generation of O(2) molecules, resulting in instability at the +c surface.     

Active thionium species mediated functionalization at the 2α-position of indole derivatives

A combination of dimethyl sulfoxide (DMSO) and trifluoroacetic anhydride (TFAA) mediates functionalization at the 2α-position of indole derivatives. Carbon and heteroatom nucleophiles were directly introduced via a one-pot procedure in excellent yields.     

Synthesis and crosslinking reaction of poly(hydroxyurethane) bearing a secondary amine structure in the main chain

This article describes the polyaddition of bifunctional five‐membered cyclic carbonates and diethylenetriamine. The polyaddition proceeded via the selective addition of the primary amino group to the cyclic carbonates to give poly(hydroxyurethane)s bearing a secondary amine structure in the main chain. The resulting poly (hydroxyurethane) having a secondary amine structure was crosslinked by a reaction with a bifunctional dithiocarbonate to give a networked poly(hydroxyurethane–mercaptothiourethane). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5899–5905, 2005     

Effects of a magnetic field on triplet-triplet annihilation in a Pt-phthalocyanine single crystal at 4.2 K

Mutual annihilation of triplet excitons in Pt-phthalocyanine single crystal at 4.2 K has been studied under magnetic fields of up to 100 kG through the measurement of the phosphorescence decay by Q-switched ruby laser excitation. The maximum annihilation rate γ which is larger than that of zero magnetic field by 40–50% is obtained at magnetic fields of 30–40 kG. The annihilation rate γ is of the order of 10⁻¹² cm³/s.     

Photoluminescence of cis- and trans-polyacetylene

The emission intensity in cis-(CH)_χ increases a little and the emission peak shifts a little to shorter wavelength with increasing temperature, which can be interpreted by the distribution of several emission centers in energy. Photoluminescence is also observed in trans-(CH)_χ at around 1.03 μm for the first time.     

Hadroproduction of heavy quark flavors in QCD

Within the framework of perturbative QCD, we investigate the hadroproduction of charmed particles via two-gluon as well as quark-pair annihilation. The total production cross section is found to be sensitive to the choice of the scale parameter Q² and in general not free from non-perturbative effects. Charmed-particle production in the high-p_T region is also studied.     

A self-consistent cluster theory of amorphous materials

A cluster method for the electronic structure of amorphous materials is presented with an application to amorphous diamond. Eight-atom cluster model gives a pseudogap in the density of states.     

Elektronenspektren von 1,1-Diphenyl?thylen und Benzophenon

Ohne Zusammenfassung     

Correlation between the hard and soft character and the visible absorption spectra of Xylenol Orange and Methylthymol Blue complexes with bivalent metal ions

The changes in the spectra of Xylenol Orange and Methylthymol Blue complexes with several bivalent metal ions have been investigated in terms of the chemical bonding between the phenolic oxygen atom and the metal ion, and the hard and soft character of the donor and acceptor. The value of this approach to indicator action is discussed.