The Accidental Cathedral : thoughts on rebuilding the energy system

Industrial Ecolog

Theory of Broensted acidity in zeolites

The nature of the chem. bond of protons in a zeolite is analyzed from theor. and spectroscopic results. Of interest is the dependence on zeolite structure as well as compn. The zeolitic OH bond is mainly covalent. Proton attachment to the zeolite lattice causes a weakening of neighboring Si-O and Al-O bonds. The effective increase in vol. of the bridging O atom causes a local deformation, that changes the strength of the lattice-chem. bonds over a few bond distances. Proton concn. effects as well as lattice-compn. effects can be understood from the lattice-relaxation model. The energetics of proton transfer is controlled by the need to stabilize the resulting Zwitter-ion. The pos. charge on the cation becomes stabilized by contact with basic lattice-O atom

Mechanism and dynamics of the CO-induced lifting of the Pt(100) surface reconstruction

The first atomistic simulations of the CO-induced lifting of the Pt(100)-hex reconstruction have been performed. During this phase transformation the surface changes back to bulk-terminated Pt(100)-(1×1), whereby the surface atom density decreases by ~20%. The simulations reveal a mechanism collective in nature, indicating that restructuring proceeds through ejection of chains of Pt atoms. These chains explain the anisotropy as seen in scanning tunneling microscopy experiments. The restructuring rate depends nonlinearly on the CO coverage, but the absence of local clustering of CO excludes an explanation in terms of elementary reaction kinetics as proposed previously

Spin dynamics in the Cu(2)-O planes of tetragonal and orthorhombic YBa2Cu3O7-delta as probed by 89Y NMR

The 89Y-nuclear relaxation rate is found to be almost similar in the orthorhombic and tetragonal modifications of YBa2Cu3O7-d. This result is seen as evidence for the unchanged spin dynamics in the Cu(2)-O planes in both compounds and as support for those theories that decouple charge and spin carriers

The conductivity and band structure of some synthetic semiconductors based on M(dmit)2 (M = Ni, Pd, Pt)

The conductivity of the following six new low-dimensional compounds is reported: (Me4N)(Ni(dmit)2), (Et4N)(Ni(dmit)2), (Pr4N)(Ni(dmit)2), (Bu4N)(Ni(dmit)2), (Bu4N)(Pt(dmit)2) and (Et4N)0.5(Pd(dmit)2). Semiconducting behaviour is found for all the compounds investigated, with activation energies between 0.1 and 0.5 eV. The crystal structures have been established by X-ray diffraction. Using these, the band structure has been determined. It is shown that the compounds investigated are semiconductors each having a correlation gap resulting from an effective electron-electron repulsion of 1.0 eV