  An extended around mean field (AMF) functional for less localized $p$
electrons is developed to quantify the influence of electronic correlations in
$\alpha$-Ga. Both the local density approximation (LDA) and generalized
gradient approximation (GGA) are known to mispredict the Ga positional
parameters. The extended AMF functional together with an onsite Coulomb
interaction of $U_{\rm eff}=1.1$ eV, as obtained from constraint LDA
calculations, reduces the deviations by about 20%. The symmetry lowering coming
along with the electronic correlations turns out to be in line with the Ga
phase diagram.
