Biomedical subjects

S T Pantelides

Publications and source records attributed to S T Pantelides.

21 records · Page 2Linked to original sources

PubMed2001

Surface reconstruction and the difference in surface acidity between gamma- and eta-alumina.

The surfaces of the gamma and eta forms of alumina are well known to differ significantly in Lewis acidity. Surface reconstructions observed on gamma- and eta-alumina are also qualitatively different, despite the close similarity of the bulk structures. Here we demonstrate through first-principles calculations that subtle differences in the bulk point defect distribution between these two forms of alumina give rise to the major differences in the mode of surface reconstruction and correlate with the different levels of Lewis acidity.

Journal Article↗

PubMed2001

Temperature effects on the transport properties of molecules.

Recent experiments found an unusual temperature-induced large shift in the resonant-tunneling voltage of certain molecules. We report first-principles calculations showing that such behavior can be caused by the excitation of rotational modes of ligands. These modes have classical characteristics, i.e., the maximum excursion is dominant, while at the same time they have a significant effect on the energy levels responsible for resonant tunneling. The proposed mechanism of ligand rotations is unique to molecules and accounts for the fact that the effect is not seen in semiconductor nanostructures.

Journal Article↗

PubMed2001

Core-hole effects on energy-loss near-edge structure.

We present first-principles electron energy-loss near-edge structure calculations that incorporate electron-hole interactions and are in excellent agreement with experimental data obtained with X-ray absorption spectroscopy (XAS) and electron energy-loss spectroscopy (EELS). The superior energy resolution in XAS spectra and the new calculations make a compelling case that core-hole effects dominate core-excitation edges of the materials investigated: Si, SiO2, MgO, and SiC. These materials differ widely in the dielectric constant leading to the conclusion that core-hole effects dominate all core-electron excitation spectra in semiconductors and insulators. The implications of the importance of core-holes for simulations of core-electron excitation spectra at interfaces will be discussed.

Journal Article↗