Ab initio structures and polarizabilities of sodium clusters

Abstract

Articles you may be interested inOn the theoretical determination of the static dipole polarizability of intermediate size silicon clusters Ab initio pseudopotential calculation of the photo-response of metal clustersWe present quantitative ab initio calculations for Na cluster structures and polarizabilities, for all cluster sizes up to 20 atoms. Our calculations are performed by combining an ab initio core-corrected pseudopotential and a gradient-corrected density functional within a real space approach. We find the cluster bonding to be very floppy and catalog a host of low-energy quasi-degenerate isomers for all second-decade clusters. The existence of these isomers results in a band of polarizability values for each cluster size even at zero temperature. This eliminates any finer structure in the polarizability curve. We further show that the experimental polarizability values are consistently underestimated by calculations at zero temperature. By computing the effects of structure expansion and distortion due to a finite temperature we arrive at a quantitative agreement between theory and experiment.

Evolution of the Structural and Electronic Properties of Medium-Sized Sodium Clusters: A Honeycomb-Like Na20 Cluster

“…But for all cluster sizes they consistently underestimate the measured values: by roughly 10 Bohr 3 for most cluster sizes. This disparity are systematically discussed in by Ma et al and Kronik et al These calculations show that the quantitative discrepancy between theory and experiment is attributed to the effect of finite temperature and geometric evolution of the clusters structure. Somewhat generalizing, the polarizability also increases as the volume occupied by the electrons .…”

Highest electron affinity as a predictor of cluster anion structures

“…Even with the most advanced search algorithms, one often finds many isomers that are very close in total energy, but differ significantly in structural and other properties. In many cases, the inter-isomer energy differences are smaller than the accuracy of common tight-binding approaches, or even density functional approaches 9,12 . In cases of doubt, a positive identification of the 'true' ground state requires tools that are in principle more accurate, but computationally very demanding, for example, quantum Monte Carlo (QMC) calculations 13 .…”

“…For obtaining low-energy metastable isomers of the clusters, we used the simulated annealing approach, implemented within the framework of Langevin molecular dynamics followed by a strict minimization of energy 4 . A detailed account of the computational approach has been provided elsewhere 12 .…”

The effect of geometry on cluster polarizability: Studies of sodium, copper, and silicon clusters at shape-transition sizes

“…Our calculated polarizability values are close to previous DFT calculations. 47,48 It is known that the computed zero-temperature polarizability for Na clusters underestimates observed values, while quantitative agreement can be achieved by taking into account thermal expansion effects. 47 The optimized structures and relative energies of the six lowest-energy Cu 16 isomers are displayed in Fig.…”