Xα,Cr2, and the symmetry dilemma

$X\alpha$ calculations (with exchange parameter $\alpha =0.7\mathrm{}$) are presented for ${\mathrm{Cr}}_2$ in which the constraint of inversion symmetry on the one-electron orbitals is avoided. The ground state is antiferromagnetic, ${}_{}{}^1{}_{}{}^{}\Sigma _{}^{+}{}_{}{}^{}$, with equilibrium separation 2.75 Å, vibrational frequency 110 ${\mathrm{cm}}^{-1\mathrm{}}$, and dissociation energy 1.0 eV. This is in qualitative agreement with the generalized-valence-bond calculation of Goodgame and Goddard.