Electrostatic interaction schemes for evaluating the polarizability of silicon clusters

Abstract

Electrostatic interaction schemes have been applied to predict the evolution of the polarizability in Si(n) clusters of increasing size (n=3-19). Both on-site polarization and charge transfer effects have been included in the interaction scheme, of which the values have been compared to B3LYP/6-311G(*) and other first principles results. To reproduce the pattern of the variation of the B3LYP average polarizability per Si atom as a function of the cluster size, the atomic polarizability employed in the interaction scheme should amount to roughly 80% of the bulk atomic polarizability. However, this results in a systematic underestimation of the polarizability per Si atom by about 25%, whereas increasing the atomic polarizability value leads to excessive variations of the polarizability per Si with the cluster size. An improved agreement is obtained when incorporating a charge transfer contribution, at least for sufficiently large clusters, substantiating the fact that in large clusters electrostatic effects are dominant over quantum effects. This charge transfer atomic polarizability term has been modeled by a simple function, which evolves linearly with the difference of Cartesian coordinates between the atom and the center of mass and that has been verified using B3LYP/6-311G(*) calculations. In the case of the prediction of the polarizability anisotropy, a similar atomic polarizability corresponding to 80% of the bulk atomic polarizability has been shown suitable to reproduce the B3LYP results, whereas inclusion of charge transfer effects can slightly improve the agreement, provided the amount of charge transfer increases with the size of the cluster.

Structures, Stabilities, and Electronic Properties of Gold Silicide Clusters: Comparison with Pure Silicon Clusters

“…Our results are in reasonable agreement with the reported experimental estimate 39.1 ± 9.8 au [56] for the gold atom and theoretical value 20 au [57] for the silicon atom. In Figure 5, the polarizability and average polarizability per atom (α/n) of small size Au 2 Si n (n = 1 -8) clusters are exhibited.…”

Study of the Structural and Electronic Properties of RhN and RuN Clusters (N < 20) within the Density Functional Theory

“…6 In other words, the isomer O h + 1 of Rh 7 with a permanent dipole moment (see Figure 5) can be expected to have a significant charge transfer among Rh atoms, thus contributing substantially to the average atomic polarizability. 40 Our calculated dipole moment for Rh 7 is smaller than 0.06 D for all the low-lyingenergy isomers, except for the capped octahedron (O h + 1) which is 0.90 (0.82) D for the state with total spin moment 11 (9) µ B . The state with total spin moment 9 µ B , is only 25 meV per atom less stable than the one with 11 µ B .…”

Effects of Changing Substituents on the Non-Linear Optical Properties of Two Coumarin Derivatives

“…Several recently published works use this technique due to the rapid convergence of NLO properties [22][23][24][25][26][27]. In the SM method, the atoms that form the surrounding molecules of the compounds are treated as point charges, since the interactions between molecules have a dominant electrostatic nature, taking into account long-range electrostatic effects [28,29]. Another alternative model to estimate χ (1) and χ (2) was proposed by Seidler and Champagne [30][31][32][33][34][35] with very good results.…”