Ionic structure effects on the optical response of lithium clusters

Abstract

Abstract. The optical response of alkali metal clusters is shown to be sensitive to a proper treatment of the electronion interaction and to the ionic spatial structure. A spherical symmetry model based on a combination of a geometrical optimization of the ionic structure and the random phase approximation (RPA) with exact exchange is applied to calculate the optical response of Li~39. The optical response obtained within this model is in good agreement with the measured giant dipole resonance.

Nonlocal ion potential effects on the optical response of lithium clusters

“…It is necessary to ensure a correct size for the Li cluster; however a minimization procedure similar to that of Ref. [4] but carried out with a nonlocal potential is a difficult numerical task. Therefore, we here abandon this selfconsistent approach to ion optimization but rather use the "inverse jellium" prescription already discussed and whose quality is illustrated in Fig.…”

“…3 the shell-like optimized radial ion density of Li~39 given by the "inverse jellium" model. Just as in our previous SAPS calculation [4], the ions occupy three well-separated shells evenly filled with 10, 40, and 89 ions, respectively. It is important to note, however, that now the radii are roughly 5 ao, 10 a0, and 15 ao, thus lower by about t5% than in Ref.…”

“…This potential inhibits penetration of the core region by valence electrons. As was already noted in our previous work [4], for lithium, which has only s core electrons, the p-wave scattering is unsatisfactorily described by such a core-repulsive pseudopotential, since this latter forces a p-cancellation in the core region while p-electrons in reality experience the full ionic potential. Thus the l dependence of the pseudopotential might be crucial.…”

“…[8,4] calculations in the case of sodium clusters, for which the electron-ion pseudopotential is essentially local (see Fig. 1 and the associated discussion in the next section).…”

“…In a previous work [4] we introduced explicitly a more realistic electron-ion pseudopotential and optimized the ion discrete distribution by minimizing the total energy. The corresponding optical response was subsequently obtained through a random phase approximation with exact exchange (RPAE) [5] that gave the correlated dipole oscillations.…”