  The present work reports results from systematic multiconfiguration
Dirac-Hartree-Fock calculations of electronic isotope shift factors for a set
of transitions between low-lying states in neutral aluminium. These electronic
quantities together with observed isotope shifts between different pairs of
isotopes provide the changes in mean-square charge radii of the atomic nuclei.
Two computational approaches are adopted for the estimation of the mass- and
field shift factors. Within these approaches, different models for electron
correlation are explored in a systematic way to determine a reliable
computational strategy and estimate theoretical error bars of the isotope shift
factors.
