AIHFLTF: Integrals in Laguerre function bases for electronic structure calculations in atoms
A program for calculating atomic integrals over Laguerre-type basis functions is provided. The Λ functions are used. They can generate complete orthonormal systems for bound states of atoms. The orthogonality property makes it possible to use large-scale basis sets without loss of accuracy. We have previously published the results of our nonrelativistic Hartree-Fock calculations for He–Og. Total energies were obtained to 30 significant figures for the atoms in the first to third periods. The integrals for this computation were calculated according to the analytical formulation given by Freund and Hill using a multiple-precision arithmetic package. This program for calculating integrals has been rewritten using Gauss-Laguerre quadrature. This version is twice as fast as the previous one while maintaining precision. Since quadruple precision arithmetic implemented in Fortran is used in this version, the program can be further accelerated by OpenMP parallelization. This version has been released.