AB-INITIO PSEUDOPOTENTIAL CALCULATION OF THE PHOTO-RESPONSE OF METAL-CLUSTERS

The photoabsorption cross section of small sodium and lithium clusters is computed in the time-dependent local density approximation to dens ity functional theory, making use of two different types of ab initio nonlocal pseudopotentials. The equilibrium geometries of the clusters have been obtained via Langevin quantum molecular dynamics. It is foun d that the average bond length of the clusters and their static polari zabilities depend on the input pseudopotential. Nonetheless, it is fou nd that the different pseudopotentials lead to the same equilibrium sh ape for the clusters, and to multipeaked line shapes for the photoabso rption cross sections which are nearly identical, apart from small ove rall energy shifts. For sodium, it is found that the local reduction o f the pseudopotential obtained by keeping only its s-part provides, in all cases, an excellent approximation to the full pseudopotential, wh ereas for lithium the same procedure proves inaccurate. (C) 1997 Ameri can Institute of Physics.