A new library for hybrid molecular integrals involving Gaussian-type and numerical orbitals

A transition-density-matrix, close-coupling approach to molecular ionization, ASTRA (AttoSecond TRAnsitions), has recently been reported in the literature. [1] A distinguishing feature of ASTRA is its use of hybrid numerical orbitals inside the molecular charge density region. The one- and two-electron integrals between these orbitals, in general multicentered, must be evaluated numerically. For many of the anticipated future applications of ASTRA involving larger molecules and/or high-energy photoionization, the efficient and accurate computation of these integrals will become a more critical issue. To address this challenge, an integral library has been developed, incorporating ideas discussed in previous work. [2] In this work, we outline the progress made integrating this library with ASTRA and elaborate on our numerical integration strategy.

[1] Randazzo J.M. et al, Phys. Rev. Res., 5, 043115 (2023)

[2] Gharibnejad H et al, CPC, 263, 107889 (2021).