291$, $Y=0.274$, and $\alpha =1$. *Upper panel*: effect of the change of the solar mixture (GN93, GS98, AS05, and AS09 ones) in the opacity tables. *Bottom panel*: effect of adopting the `OPAL` 2006 and `PTEH` EOS.[]{data-label="fig:inputs1"}](EpsiLi_mixtures_new.eps "fig:"){width="\linewidth"} ![Comparison among the surface lithium abundance obtained with our reference set of tracks (*solid line*) and models with different assumptions on the adopted physical inputs, for M = 0.6, 0.8, 1.0, and 1.2 M$_\odot$ with $Z=0.01291$, $Y=0.274$, and $\alpha =1$. *Upper panel*: effect of the change of the solar mixture (GN93, GS98, AS05, and AS09 ones) in the opacity tables. *Bottom panel*: effect of adopting the `OPAL` 2006 and `PTEH` EOS.[]{data-label="fig:inputs1"}](EpsiLi_EOS_new.eps "fig:"){width="\columnwidth"}

Opacity coefficients.
---------------------

Besides the influence on the opacity of the heavy element distribution, it is worth analysing the error on the calculation of Rosseland radiative opacity coefficients $\kappa_\mathrm{R}$ at fixed chemical composition. The current version of the opacity tables we adopt in present calculations [i.e. `OPAL` 2005 see e.g., @rogers92; @iglesias96] does not contain information about the related uncertainty. Thus to give a conservative uncertainty estimation on $\kappa_\mathrm{R}$, we evaluated the relative differences between the `OPAL` and the `OP` [*Opacity Project* see e.g, @seaton94; @badnell05] radiative opacity coefficients in their full range of validity, once the same chemical composition has been adopted. We found that the maximum/minimum relative difference between the two opacity tables is close to $\pm 5\%$ in the region of interest for the present calculations (i.e. the convective envelope) [see also, @neuforge01; @badnell05; @valle12]. Thus, we assume the value of $\Delta\kappa_\mathrm{R}/\kappa_\mathrm{R} = \pm5 \%$ as a conservative uncertainty.

Equation of state
-----------------

Owing to the complexity of the evaluations of the various thermodynamical 