Acoustic vibrations of anisotropic nanoparticles

TL;DR

This paper theoretically investigates the acoustic vibrations of anisotropic and non-spherical nanoparticles using continuum models, providing tools for mode classification and insights into vibrational behaviors relevant for Raman scattering.

Contribution

It introduces a comprehensive theoretical framework for analyzing vibrational modes of anisotropic, non-spherical nanoparticles, including classification tools and mode evolution analysis.

Findings

Modes evolve continuously from isotropic sphere vibrations

Tools for identifying modes with significant Raman scattering cross-section

Qualitative insights into mode nature based on symmetry and shape

Abstract

Acoustic vibrations of nanoparticles made of materials with anisotropic elasticity and nanoparticles with non-spherical shapes are theoretically investigated using a homogeneous continuum model. Cubic, hexagonal and tetragonal symmetries of the elasticity are discussed, as are spheroidal, cuboctahedral and truncated cuboctahedral shapes. Tools are described to classify the different vibrations and for example help identify the modes having a significant low-frequency Raman scattering cross-section. Continuous evolutions of the modes starting from those of an isotropic sphere coupled with the determination of the irreducible representation of the branches permit some qualitative statements to be made about the nature of various modes. For spherical nanoparticles, a more accurate picture is obtained through projections onto the vibrations of an isotropic sphere.