  Atomic diffusion in stars can create systematic trends of surface abundances
with evolutionary stage. Globular clusters offer useful laboratories to put
observational constraints on this theory as one needs to compare abundances in
unevolved and evolved stars, all drawn from the same stellar population. In
this paper, we show the results of an abundance study of stars in the globular
cluster NGC6752 which shows weak but systematic abundances trends with
evolutionary phase for Fe, Sc, Ti and Ca. The trends are best explained by a
stellar structure model including atomic diffusion with efficient additional
mixing. The model allows to correct for sub-primordial stellar lithium
abundances of the stars on the Spite plateau, and to match it to the
WMAP-calibrated Big-Bang nucleosynthesis predictions to within the mutual
1-sigma errors.
