The atomic structure of dioctahedral 2:1 phyllosilicate edge surfaces was calculated using pseudopotential planewave density functional theory. Bulk structures of pyrophyllite and ferripyrophyllite were optimized using periodic boundary conditions, after which crystal chemical methods were used to obtain initial terminations for ideal (110)and (010)-type edge surfaces. The edge surfaces were pr...

Antiferromagnetic spin chains have been the subject of intense interest in recent years, largely due to the conjecture by Haldane that chains built from integer spins should exhibit a gap in their energy spectrum. The existence of this gap, originally predicted on the basis of simple fieldtheoretic considerations, was subsequently confirmed experimentally. Much insight into the properties of an...

Chemical bonding is the stabilization of a molecular system by charge- and spin-reorganization processes in chemical reactions. These processes are said to be local, because the number of atoms involved is very small. With multi-configurational self-consistent field (MCSCF) wave functions, these processes can be calculated, but the local information is hidden by the delocalized molecular orbita...

Using two different molecular orbital methods which treat all valence electrons, namely extended Huckel theory and CNDO/2,a correlation has been found between the biological activity of cephalosporin derivatives and certain aspects of the electronic structure of the /3lactam ring. Electron populations of the carbonyl carbon and bond strength indices of both the carbonyl carbon-nitrogen bond and...

The pressure-dependent relation between Eu valence and lattice structure in model compound EuO is studied with synchrotron-based x-ray spectroscopic and diffraction techniques. Contrary to expectation, a 7% volume collapse at ≈45  GPa is accompanied by a reentrant Eu valence transition into a lower valence state. In addition to highlighting the need for probing both structure and electronic sta...