Title

Anomalously Soft And Stiff Modes Of Transition-Metal Nanoparticles

Abstract

We propose an explanation for the enhanced low- and high-energy tails of the vibrational density of states (VDOS) of nanoparticles (NPs) with respect to their bulk counterparts. Density functional theory calculations of the frequency and eigenvector of each mode allow us to identify radial breathing/multipolar and nonradial tidal/shear/torsional vibrations as the modes that populate such tails. These modes have long been obtained from elasticity theory and are thus analogous to the widely studied and observed pulsations in variable stars. The features particular to the VDOS of NPs are rationalized in terms of the charge density distribution around low-coordinated atoms, the quasi-radial geometric distribution of NPs, force constant variations, degree of symmetry of the nanoparticle, discreteness of the spectrum, and the confinement of the eigenmodes. Our results indicate that the high- and low-energy tails of the VDOS may be a powerful tool to reveal information about the chemical composition and geometric structure of small NPs. In particular, the size of the confinement gap at the low-frequency end of the VDOS and the extent by which the high-frequency end surpasses the bulk limit signal whether a NP is bulk-like or non-bulk-like and the extent to which it is disordered. © 2014 American Chemical Society.

Publication Date

5-15-2014

Publication Title

Journal of Physical Chemistry C

Volume

118

Issue

19

Number of Pages

10335-10347

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1021/jp409956e

Socpus ID

84900804637 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/84900804637

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