Vibrations of Au-13 and FeAu12 nanoparticles and the limits of the Debye temperature concept

    Authors

    G. Shafai; M. A. Ortigoza;T. S. Rahman

    Comments

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    Abbreviated Journal Title

    J. Phys.-Condes. Matter

    Keywords

    TOTAL-ENERGY CALCULATIONS; GOLD CLUSTERS; MOLECULAR-DYNAMICS; DEPENDENCE; CHEMISTRY; CATALYSIS; COPPER; SIZE; Physics, Condensed Matter

    Abstract

    We present first-principles calculations of the vibrational density of states (VDOS), the specific heat and the mean-squared displacement of the five lowest-energy isomers of Au-13 and of two low-energy FeAu12 nanoparticles. We find that the vibrational contributions to the Helmholtz energy do not affect the energy ordering of the isomers. As expected, for nanoparticles the vibrational density of states differs dramatically from the function proposed by the Debye model. We demonstrate that, for the nanoclusters we studied, the alternative calculations of the 'Debye temperature' yield significantly inconsistent results. We conclude that T-D obtained from a particular thermodynamic property is neither applicable for deriving conclusions about other thermodynamic properties nor correlated with atomic bond strengths. Instead, in order to describe the temperature dependence of a nanoparticle's mean-squared displacement and its specific-heat capacity, what is necessary is its discrete phonon spectrum.

    Journal Title

    Journal of Physics-Condensed Matter

    Volume

    24

    Issue/Number

    10

    Publication Date

    1-1-2012

    Document Type

    Article

    Language

    English

    First Page

    8

    WOS Identifier

    WOS:000301176300029

    ISSN

    0953-8984

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