Selected configuration interaction at the exascale within an integral driven framework

Selected Configuration Interaction (sCI) is a multireference many-body method for accurate calculations of properties of ground- and excited-state wavefunctions, achieved by expanding the system's wavefunction within the space of its Slater determinants. While sCI's strength lies in its ability to converge to the full CI limit through iterative refinement to the reference wavefunction, it inherently faces computational challenges, stemming from large active spaces and the sheer volume of required electron repulsion integrals for systems with many active orbitals.

In this presentation, we will discuss ARCHES, our recent implementation of a modern sCI framework suitable for exascale calculations and next generation quantum chemistry and materials science calculations. Our framework is built to flexibly handle both distributed parallelization and computational offloading with GPUs, relying upon an integral-driven approach in which the electron repulsion integrals are distributed across workers. We will discuss our approach for optimizing performance in modern HPC settings across several benchmark studies and showcase capabilities of ARCHES such as the calculation of spectral densities within a Green's function approach.