Understanding the behaviour of the atomic nucleus

The nuclear shell model

Due to the complexity of the nuclear interaction, it is not possible to calculate nuclear properties from first principles – one has to resort to models that grasp the most important physics for a given nucleus. A very successful approach is the nuclear shell model, for which the full-scale many-body problem is reduced to an inert “core” and a few valence particles. Even with such a simplified model, calculations are not feasible for many cases as one quickly runs out of both memory and CPU power. 

Calculating the properties

At the HPC project gRESONANT we use the code ‘’KSHELL’’ to model the atomic nucleus using the nuclear shell model. With this code, we can calculate properties of the atomic nucleus, such as energy, spin, and parity. We study the decay properties of certain isotopes of the medium-mass nuclei scandium, titanium and vanadium in an effort to understand experimental data that has so far remained unexplained. In turn, these properties will impact our understanding of astrophysical neutron-capture reaction rates needed for the element nucleosynthesis in stars and neutron-star collisions.

Utilizes Betzy's parallelism

KSHELL is a highly parallelizable application that greatly benefits of the large number of cores on supercomputer Betzy. KSHELL scales well at up to 128 nodes which amounts to 16384 CPU cores, and the node count can be pushed even higher, still yielding good results. A hybrid OpenMP + MPI implementation delivers the best performance and using SMT decreases the computation time by up to 20%. Due to the sheer sizes of our calculations with respect to memory and CPU requirements, they would simply not be possible without Betzy!