  We analyse for the first time the radial abundance gradients of the disc
stars of a disc galaxy simulated with our three dimensional, fully cosmological
chemodynamical galaxy evolution code GCD+. We study how [Fe/H], [N/O], [O/Fe],
[Mg/Fe] and [Si/Fe] vary with galactocentric radius. For the young stars of the
disc, we found a negative slope for [Fe/H] and [N/O] but a positive [O/Fe],
[Mg/Fe] and [Si/Fe] slope with radius. By analysing the star formation rate
(SFR) at different radii, we found that the simulated disc contains a greater
fraction of young stars in the outer regions, while the old stars tend to be
concentrated in the inner parts of the disc. This can explain the positive
[alpha/Fe] gradient as well as the negative [N/O] gradient with radius. This
radial trend is a natural outcome of an inside-out formation of the disc,
regardless of its size and can thus explain the recently observed positive
[alpha/Fe] gradients in the Milky Way disc open clusters.
