Anomalously Soft and Stiff Modes of Transition-Metal Nanoparticles

    Authors

    M. A. Ortigoza; R. Heid; K. P. Bohnen;T. S. Rahman

    Comments

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    Abbreviated Journal Title

    J. Phys. Chem. C

    Keywords

    TOTAL-ENERGY CALCULATIONS; VIBRATIONAL DYNAMICS; NONRADIAL OSCILLATIONS; MOLECULAR-DYNAMICS; LATTICE-VIBRATIONS; LINEAR-RESPONSE; SURFACE MODES; STARS; SIZE; NANOCRYSTALS; Chemistry, Physical; Nanoscience & Nanotechnology; Materials Science, ; Multidisciplinary

    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 nonraclial 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.

    Journal Title

    Journal of Physical Chemistry C

    Volume

    118

    Issue/Number

    19

    Publication Date

    1-1-2014

    Document Type

    Article

    Language

    English

    First Page

    10335

    Last Page

    10347

    WOS Identifier

    WOS:000336198900056

    ISSN

    1932-7447

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