A General Toolbox for the Calculation of Higher-Order Molecular Properties Using SCF Wave Functions at the One-, Two- and Four-Component Levels of Theory

We outline a new approach for the calculation of higher-order molecular properties for self-consistent field (SCF) wave functions (or Kohn-Sham density-functional theory) expressed in time-and perturbation-dependent basis sets. The approach is based on an atomic-orbital-based, open-ended quasienergy derivative formalism, and is applicable for use in linear scaling SCF calculations. In order to enable the calculation of any response property, we have also developed open-ended one-and two-electron integral derivative programs, as well as a program that can calculate derivatives of exchange-correlation functionals to any order using automatic differentiation. These modules have been interfaced to both the Dalton and DIRAC programs. This allows us to calculate molecular properties at the one-, two- and four-component levels of theory using a common theoretical framework and code.