Enabling Linear Scaling Exact Exchange for Heterogeneous Systems

Hybrid functionals reduce the self-interaction error in semi-local density functional theory (DFT) and provide a semi-quantitative description of the electronic structure in systems throughout chemistry, physics, and materials science. However, the high computational cost associated with evaluating the exact exchange (EXX) interaction limits hybrid DFT from treating large-scale condensed-phase systems. To address this challenge, we have developed a linear-scaling real-space approach that exploits the sparsity in the EXX interaction using local orbitals (MLWFs). The resulting massively parallel algorithm (exx) provides an accurate evaluation of all EXX quantities and enables hybrid DFT based ab initio molecular dynamics (AIMD) of large-scale finite-gap systems with a wall time cost comparable to semi-local DFT [1]. Since exx was optimized to treat homogeneous systems, its performance degrades when treating highly anisotropic heterogeneous systems with multiple phases and/or components. In this work, we discuss three major theoretical and algorithmic advances that enable efficient and accurate hybrid DFT based AIMD of large-scale heterogeneous systems, and showcase the extended exx module when treating a complex solid-liquid interface.
[1] J Chem Theory Comput 16, 3757 (2020).