Quantification of the basis set error for molecules in strong magnetic fields and general orientation

The paper investigates the basis set incompleteness errors (BSIE) of the Hartree- Fock (HF) wave function for molecules in extreme magnetic field strengths up to 5 B0 (≈ 10^6 T), considering electronic state, geometric structure, and orientation of the molecule with respect to the magnetic field direction. We compare the results from finite-field calculations using uncontracted correlation consistent basis sets with the fully numerical solution using multiresolution analysis (MRA) on the He atom and its dimer, as well as the methylidyne radical and the water molecule. Standard uncontracted aug-cc-pVQZ basis sets are generally reliable up to B = 0.2 B0. Between B = 0.5 B0 and 1.0 B0 care must be taken as the ground state switches to states with high multiplicities for which standard basis sets have not been optimized. Beyond B = 1.0 B0 the angular and state dependence of these basis sets becomes too large and too unsystematic for results to be considered reliable.