Using a Hubbard Hamiltonian treated in the Hartree-Fock approximation,
it is proposed that the (2 x 1) reconstruction of Si(001) is stabiliz
ed by a two-dimensional (2 x 2) antiferromagnetic ordering of magnetic
moments on the dimers. This provides a consistent explanation of the
semiconducting character of the Si(001) surface without invoking any a
symmetry of the dimers. These results are in agreement with a recent w
ork by Artacho and Yndurain.