Simple DFT - LSDA Modelling of theMolecular - like Aspects of Ultra - thin FilmPropertiesBy

Ordered ultra-thin Films (UTF's) are atomic n-layers (n = 1; 2; 3; : : :) with translational symmetry in-plane and molecular-like inter-planar spacings. Though commonly used (especially at relatively large n-values) as models of crystalline surfaces, they are intrinsically interesting and of growing technological signiicance as the basic building blocks of multi-layer electronic devices. Predicting the structure and properties of even a simple diatomic 1-layer means addressing aspects of molecular binding (and boundary conditions) in the context of an extended, periodically bounded system. At the level of reenement provided by the local spin density approximation to Density Functional Theory, the baseline standard of today's predictive, chemically speciic solid-state calculations, a number of technical and fundamental issues arise. We focus on treatment of the isolated atoms, on basis sets, and on numerical precision, as illustrated by the Fe atom and BN 1-and 2-layer calculations. Computational requirements are illustrated by a brief summary of recently completed calculations on crystalline corundum,-Al2O3, which used the same code.