Scalable Codes for Precision Calculations of Properties of Complex Atomic Systems

Abstract

High precision atomic data are indispensable for studies of fundamental symmetries, tests of fundamental physics postulates, developments of atomic clocks, ultracold atom experiments, astrophysics, plasma science, and many other fields of research. We have developed a new parallel atomic structure code package that enables computations that were not previously possible due to system complexity. This code package also allows much quicker computations to be run with higher accuracy for simple systems. We explored different methods of load-balancing matrix element calculations for many-electron systems, which are very difficult due to the intrinsic nature of the computational methods used to calculate them. Furthermore, dynamic memory allocation and MPI parallelization have been implemented to optimize and accelerate the computations. We have achieved near-perfect linear scalability and efficiency with the number of processors used for calculation, paving the way towards the future where most open-shell systems will finally be able to be treated with good accuracy. We present several examples illustrating new capabilities of the newly developed codes, specifically correlating up to all 60 electrons in the highly charged Ir17+ ion and predicting certain properties of Fe16+.

Many-Electron QED with Redefined Vacuum Approach

“…In recent years, the accuracy of large-scale correlation calculations of transition energies in many-electron atoms and ions drastically improved [2,44,[53][54][55][56]. Various highly efficient computer codes have been developed for this purpose [57][58][59][60][61][62]. In view of this rapid progress, it becomes increasingly important to include the QED effects in these calculations as well.…”

Many-Electron QED with Redefined Vacuum Approach

“…In recent years, the accuracy of large-scale correlation calculations of transition energies in many-electron atoms and ions drastically improved [2,33,[42][43][44][45]. Various highly efficient computer codes have been developed for this purpose [46][47][48][49][50][51]. In view of this rapid progress, it becomes increasingly important to include the QED effects in these calculations as well.…”

Low-lying energy levels of ^{229}Th35+ and the electronic bridge process

“…To carry out these calculations for such a complicated open-shell system as Th 35+ we used a new parallel atomic structure code package developed and described in Ref. [13]. This package (i) allows us much quicker computations and (ii) enables to work with a CI space of a much larger size than was possible previously when we used serial versions of the programs.…”