Phonon spectrum and vibrational characteristics of linear nanostructures in solid matrices

TL;DR

This paper investigates the phonon spectrum and vibrational properties of linear nanostructures embedded in solid matrices, revealing quasi-one-dimensional behavior and analyzing vibrational contributions to low-temperature heat capacity.

Contribution

It provides a detailed analysis of phonon spectra and vibrational characteristics of linear chains in matrices, highlighting the transition to quasi-1D behavior and its effects.

Findings

Quasi-1D features are typical when interatomic interactions dominate.

Transition to quasi-1D behavior occurs at the van Hove singularity.

Vibrational contributions significantly affect low-temperature heat capacity.

Abstract

The atomic dynamics of linear chains embedded in a crystalline matrix or adsorbed on its surface is studied. A linear chain formed by substitutional impurities in a surface layer and at the same time offsetting from this layer was analyzed particularly. This system models the actively studied experimentally structures in which gas molecules are adsorbed on the walls of the bundles of carbon nanotubes located in certain medium. It is shown that the quasi-1D features are typical for the chains in which the interatomic interaction is higher than the interaction between the atoms of the chain and the atoms of the crystal matrix. On the local phonon density of atoms of the chain, the transition to quasi-one-dimensional behavior has the form of the kink. In other words, it is the first (lowest-frequency) van Hove singularity, which in 3D structures (the system under consideration is generally three-dimensional) corresponds to the transition from closed to open constant-frequency (quasi-plane) surfaces. The local phonon densities of atoms in the chain have one-dimensional character at frequencies higher than the frequency of the van Hove singularity. The rms-amplitude of embedded chains atoms vibrations is calculated and the behavior of the atomic vibrations contribution in the low-temperature heat capacity of the system is analyzed.