Abstract details

We have computed new models for stars of low and intermediate mass with varying degrees of $\alpha$-element enhancement factors. For this purpose, new low-temperature molecular opacities have been computed and combined with consistent high-temperature OPAL opacities. We found that old $\alpha$-rich low-T tables were erroneous, but that this influences the models only at solar- and super-solar metallicities. At high temperatures, the different enhancement factors do influence the core structures and can lead to significantly different main sequence lifetimes. The consequence for population synthesis could be that not only the overall level of $\alpha$-enhancement must be known, but also individual abundances.