Complete line list and solar values

At variance with intermediate-age and old open clusters, for which a conspicuous number of studies is now available, until a few years ago clusters younger than 150Myr had been mostly overlooked in terms of their chemical composition (with few exceptions). On the other hand, previous investigations seem to indicate an anomalous behaviour of young clusters, which include (but is not limited to) slightly sub-solar iron (Fe) abundances and extreme, unexpected barium (Ba) enhancements.

In a series of papers, we plan to expand our comprehension of this topic and investigate whether these chemical peculiarities are instead related to abundance analysis techniques. We present here a new determination of the atmospheric parameters for 23 dwarf stars observed by the Gaia-ESO survey in five young open clusters (age less than 150Myr) and one star forming region (NGC 2264). We exploit a new method based on titanium (Ti) lines to derive spectroscopic surface gravity and, most important, microturbulence parameter.