The discovery of new materials has historically been a driving force for advancements in technology. Through progress in theoretical understanding and experimental control, new materials can now be designed at the atomic level. This will lead to a new class of materials, Quantum Materials, where quantum mechanical effects manifest on macroscopic scales [1]. There is a national commitment to study the fundamental science of quantum materials, as recognized by the recent NWO gravitation programme “Materials for the Quantum Age – QuMat” [2].

Quantum Materials require a quantum description. To this end, we use first principles simulations that can capture the material specific details at the quantum level. In this talk we focus on two state-of-the-art applications, first-principles superconductivity and theoretical spectroscopy. Our group is proactively developing theory and implementing it in open-source codes SIESTA [3-5] and YAMBO [6-8], respectively. We then use these codes, among others, to study realistic systems involving interfaces, defects and heterostructures consisting of tens to hundreds of atoms. To scale the codes to these system sizes, the availability of High Performance Computing (HPC) facilities is essential.

We discuss our approaches to run these codes efficiently on HPC resources. In particular, we show how the codes exploit parallelism and distributed memory, and the need for good built-in heuristics to distribute the workload. We also talk about the trend of modular code design that allows the offloading of the most expensive operations to highly optimized libraries like OpenBLAS, ELPA and ELSI [9,10]. In addition to code optimization, we also discuss the importance of good tooling and information resources. From proper documentation and code maintenance to reproducible build tools like EasyBuild and Spack and workflow managers like AiiDA [11]. We finally highlight the recent development of porting routines to GPUs to further accelerate simulations [5, 7, 12].

References
[1] B. Keimer and J. E. Moore, The physics of quantum materials, Nature Physics 13, 1045 (2017)
[2] Materials for the Quantum Age – QuMat, https://qumat.org/
[3] R. Reho, N. Wittemeier, A. H. Kole, P. Ordejón, Z. Zanolli, Density functional Bogoliubov-de Gennes theory for superconductors implemented in the SIESTA code,
https://doi.org/10.48550/arXiv.2406.02022
to appear in Phys. Rev. B, 2024
[4] J. M. Soler et al., The SIESTA method for ab initio order-N materials simulation, J. Phys.: Condens. Matter 14(11), 2745–2779 (2002)
[5] A. García et al., Siesta: Recent developments and applications, J. Chem. Phys 152(20), 204108 (2020)
[6] A. Marini et al., yambo: An ab initio tool for excited state calculations, Computer Physics Communications 180, 1392 (2009)
[7] D. Sangalli et al., Many-body perturbation theory calculations using the yambo code, Journal of Physics: Condensed Matter 31, 325902 (2019)
[8] R. Reho, A. R. Botello-Méndez, D. Sangalli, M. J. Verstraete, Zeila Zanolli, Excitonic response in transition metal dichalcogenide heterostructures from first principles: Impact of stacking, twisting, and interlayer distance, Phys Rev B 110, 035118 (2024)
[9] T. Auckenthaler et al., Parallel solution of partial symmetric eigenvalue problems from electronic structure calculations, Parallel Computing 27(12), 783-794 (2011)
[10] V. W.-z. Yu et al., ELSI: A Unified Software Interface for Kohn-Sham Electronic Structure Solvers, Computer Physics Communications 222, 267-285 (2018)
[11] S.P. Huber et al., AiiDA 1.0, a scalable computational infrastructure for automated reproducible workflows and data provenance, Sci Data 7, 300 (2020)
[12] Ivan Carnimeo et al., Quantum ESPRESSO: One Further Step toward the Exascale, Journal of Chemical Theory and Computation 19(20), 6992-7006 (2023)

Authors: A. H. Kole, A. R. Botello-Méndez, Zeila Zanolli