Why model high-k dielectrics?

New dielectrics need more than a high dielectric constant. They need to satisfy various constraints concerning band offsets, limits on charge traps, processability, reproducibility, and stability against degradation and breakdown. It seems unlikely that purely empirical approaches will produce a dielectric which justifies major investment. I discuss some of the atomistic modelling which can aid selection, and which might indicate routes around some of the interface-related and defect-related problems. These include diffusion during processing or in operation, the use of interface engineering to adjust band offsets, and the issues of crystallinity and of stoichiometry.