On the electric dipole moments of small sodium clusters from different theoretical approaches

作者：Aguado Andres; Largo Antonio; Vega Andres; Carlos Balbas Luis

来源：Chemical Physics, 2012, 399: 252-257.

DOI：10.1016/j.chemphys.2011.07.032

• Metallic clusters
• Dipole moment
• Polarizability
• Density functional theory
• van der Waals interaction
• MR-CI calculations

The dipole moments of Na-n clusters in the size range 10 %26lt; n %26lt; 20, recently measured at very low temperature (20 K), are much smaller than predicted by standard density functional methods. On the other hand, the calculated static dipole polarizabilities in that range of sizes deviate non-systematically from the measured ones, depending on the employed first principles approach. In this work we calculate the dipole moments and polarizabilities of a few isomers of Nan clusters of selected sizes (n = 13, 14, 16), obtained recently through an extensive unbiased search of the global minimum structures, and using density functional theory methods as well as ab initio MP2, CASSCF, and MR-CI methods. Among the density functional approaches, we consider the usual local density and generalized gradient approximations, as well as a recent van der Waals self-consistent functional accounting for non-local dispersion interactions. Both non-local pseudopotentials and all-electron implementations are employed and compared in order to assess the possible contribution of the core electrons to the electric dipole moments. Our new geometries possess significantly smaller electric dipole moments than previous density functional results, mostly when combined with the van der Waals exchange-correlation functional. However, although the agreement with experiment clearly improves upon previous calculations, the theoretical dipole moments are still about one order of magnitude larger than the experimental values, suggesting that the correct global minimum structures have not been located yet.

• 出版日期2012-5-3