Electronic structure and magnetic susceptibility of monoclinic $\alpha$-plutonium

The electronic structure of the $\alpha$-phase of plutonium has been calculated by the band methods with allowance for the spin-orbit interaction and Coulomb correlations in the complete matrix form (the LDA+U+SO method). The strong spin-orbit interaction of the $5f$ electrons is manifested in the splitting of the calculated density of the $5f$ states, which makes a small contribution at the Fermi level on the order of the contribution from the $6d$ states. Using the results of the ab initio calculations, the spin and orbit contributions to the magnetic susceptibility of б-plutonium have been determined. Along with the impurity contribution, they describe well the experimental data on the susceptibility of this plutonium phase to a temperature of $300$ K.