1994A&A...285..473F

New evolutionary sequences for low-mass (0.5M_☉ ≤M_* ≤ 2.5M_☉) pre-main sequence stars of two different metallicities (Z = 0.02 and 0.04) are presented, making use of the most recent physical ingredients. Nucleosynthesis is also followed in detail. Furthermore, we determine the theoretical uncertainties engendered by various treatments of the surface conditions that significantly affect predictions concerning the evolution and the light element surface depletion of these stars. The detailed comparison with observations mainly indicate that (i) it is quite hazardous to determine masses of T Tauri stars with a precision of less than about 0.3M_☉ given the theoretical uncertainties, (ii) the same conclusion holds, to a less extent, for age determinations, especially if the metallicity of the observed stars is not accurately measured and (iii) while we find a very good agreement with the observed Li - T_effcorrelation for the Hyades open cluster, we overestimate the level of Li depletion for the Pleiades. Suggestions are made about this problem. More particulary, at the end of the pre-main sequence phase, our solar model (that we fit with α= 1.5 and Z/X = 0.02744) still keeps in the convective envelope 34% of its initial ⁷Li content. This is quite lower than some of the other works with which we have compared.