Context : 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 .

Aims : Atomic diffusion and additional mixing has been shown to be at work in the globular cluster NGC 6397 at a metallicity of \left [ \mbox { Fe / H } \right ] \sim - 2.1 .
We investigate possible abundance trends in Li , Mg , Ca , Ti , Sc , and Fe with evolutionary stage in another globular cluster NGC 6752 at a metallicity of \left [ \mbox { Fe / H } \right ] \sim - 1.6 .
This in order to better constrain stellar structure models including atomic diffusion and additional mixing .

Methods : We performed a differential abundance analysis on VLT/FLAMES-UVES data of 16 stars in four groups between the turnoff point and the red giant branch .
Continuum normalisation of the stellar spectra was performed in an automated way using DAOSPEC .
Differential abundances relative to the sun were derived by fitting synthetic spectra to individual lines in the stellar spectrum .

Results : We find weak systematic abundance trends with evolutionary phase for Fe , Sc , Ti , and Ca .
The individual trends are weaker than the trends in NGC 6397 and only significant at the 1- \sigma level .
However , the combined trend shows a significance on the 2- \sigma level .
The trends are best explained by stellar-structure models including atomic diffusion with more efficient additional mixing than needed in NGC 6397 .
The model allows to correct for sub-primordial stellar lithium abundances of the stars on the Spite plateau .

Conclusions : Abundance trends for groups of elements , differently affected by atomic diffusion and additional mixing , are identified .
Although the significance of the trends is weak , they all seem to indicate that atomic diffusion is operational along the evolutionary sequence of NGC 6752 .
The trends are weaker than those observed in NGC 6397 , which is perhaps due to more efficient mixing .
Using models of atomic diffusion including efficient additional mixing , we find a diffusion-corrected primordial lithium abundance of \log \varepsilon ( Li ) = 2.58 \pm 0.10 , in agreement with WMAP-calibrated Big-Bang nucleosynthesis predictions within the mutual 1- \sigma uncertainties .