Pseudopotential calculation of the screening of a helium atom in aluminium

The screening of a helium atom embedded in an electron gas with a density appropriate to aluminium has been calculated in a linear approximation. The helium impurity was represented by a pseudopotential of the Austin form. The total charge is expressed as the sum of three components: the helium core charge density the orthogonalisation hole and the linear screening charge. The calculated charge density in the vicinity of the nucleus agrees well with the results of a recent nonlinear screening calculation of Whitmore. At longer range, the two calculations differ by a phase shift in the Friedel oscillations. Both the linear and the nonlinear screening calculations are compared with a recent Green function calculation by Inglesfield and Pendry. Their results exhibited a much smaller orthogonalisation hole than was found in the other two calculations. He-Al interatomic potentials were calculated based on both linear and nonlinear screening. The results are in reasonable agreement in the repulsive region.