Open and anisotropic soft regions in a model polymer glass
arXiv:2104.10411 · doi:10.3390/polym13081336
Abstract
The vibrational dynamics of a model polymer glass is studied by Molecular Dynamics simulations. The focus is on the "soft" monomers with high participation to the lower-frequency vibrational modes contributing to the thermodynamic anomalies of glasses. To better evidence their role, the threshold to qualify monomers as soft is made severe, allowing for the use of systems with limited size. A marked tendency of soft monomers to form quasi-local clusters involving up to 15 monomers is evidenced. Each chain contributes to a cluster up to about three monomers and a single cluster involves monomer belonging to about 2-3 chains. Clusters with monomers belonging to a single chain are rare. The open and tenuous character of the clusters is revealed by their fractal dimension . The inertia tensor of the soft clusters evidences their strong anisotropy in shape and remarkable linear correlation of the two largest eigenvalues. Owing to the limited size of the system, finite-size effects, as well as dependence of the results on the adopted polymer length, cannot be ruled out.
References in corpus (18)
- Irreversible reorganization in a supercooled liquid originates from localised soft modes
- Harmonic Vibrational Excitations in Disordered Solids and the "Boson Peak"
- Vibrational modes identify soft spots in a sheared disordered packing
- Anharmonicity, vibrational instability and Boson peak in glasses
- Continuum limit of the vibrational properties of amorphous solids
- Statistics and properties of low-frequency vibrational modes in structural glasses
- Inhomogeneous elastic response of silica glass
- The evolution of vibrational excitations in glassy systems
- Low-frequency vibrational modes of stable glasses
- Local inversion-symmetry breaking controls the boson peak in glasses and crystals
- Universal non-phononic density of states in 2D, 3D and 4D glasses
- Diffusion- and reaction-limited cluster aggregation revisited
- Localised soft modes and the supercooled liquid's irreversible passage through its configuration space
- Anomalous vibrational properties in the continuum limit of glasses
- Probing the non-Debye low frequency excitations in glasses through random pinning
- Interpretation of the vibrational spectra of glassy polymers using coarse-grained simulations
- Scaling between structural relaxation and caged dynamics in Ca_{0.4}K_0.6(NO_{3})_{1.4} and glycerol: free volume, time scales and implications for the pressure-energy correlations
- Boson Peak decouples from elasticity in glasses with low connectivity