Earlier this month the first annual meeting of the French working group NBODY (GDR NBODY) took place in Lille. Since the GDR NBODY is an association of interdisciplinary scientists working on N-body problems in chemistry an physics, the about 80 participants came from a broad background ranging from quantum chemistry, materials science, mathematics or nuclear physics. The overall atmosphere of the conference was extremely relaxed, such that during the talks vivid discussions frequently arose. I particularly enjoyed the presentations about N-body effects in nuclear physics and the first-principle simulations of the structure of nuclei, since that topic was completely new to me. Fortunately there was one introductory talk for each of the four mayor topics of the working group bringing everyone up to speed in each others' subject.

As part of the program I presented about DFTK and our recent advances with the code. I first gave a brief rationalisation why we started DFTK as a new code for working on electronic-structure problems from the mathematical perspective, then I briefly presented two applications, where we hope our code could be useful towards developing new approaches for practical calculations. One is an investigation of increased precision and more generally estimates for the floating-point error in density-functional theory calculations. The other was a discussion of our ongoing work on SCF preconditioning techniques. In this I showed our first steps towards developing a mathematically justified SCF preconditioner suitable for tackling systems containing both a conducting and an insulating part. Our first results indicate that our approach could be more suitable than established methods, which usually rely on interpolating empirically between the established preconditioning strategies for metals and insulators. Our hope would be that our preconditioner could allow to apply DFTK in the context of simulating the electronic structure of catalytic metal surfaces in the future. In this application a challenge for SCF schemes is that employed catalysts are usually coated with an insulating oxide layer or are interfacing with more insulating organic compounds or air.

Link
Using the density-functional toolkit (DFTK) to investigate floating-point error and SCF convergence (Slides)