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The ω3 scaling of the vibrational density of states in quasi-2D nanoconfined solids.

Published version
Peer-reviewed

Type

Article

Change log

Authors

Yang, Chenxing 
Phillips, Anthony E  ORCID logo  https://orcid.org/0000-0003-4225-0158
Zaccone, Alessio 

Abstract

The vibrational properties of crystalline bulk materials are well described by Debye theory, which successfully predicts the quadratic ω2 low-frequency scaling of the vibrational density of states. However, the analogous framework for nanoconfined materials with fewer degrees of freedom has been far less well explored. Using inelastic neutron scattering, we characterize the vibrational density of states of amorphous ice confined inside graphene oxide membranes and we observe a crossover from the Debye ω2 scaling to an anomalous ω3 behaviour upon reducing the confinement size L. Additionally, using molecular dynamics simulations, we confirm the experimental findings and prove that such a scaling appears in both crystalline and amorphous solids under slab-confinement. We theoretically demonstrate that this low-frequency ω3 law results from the geometric constraints on the momentum phase space induced by confinement along one spatial direction. Finally, we predict that the Debye scaling reappears at a characteristic frequency ω× = vL/2π, with v the speed of sound of the material, and we confirm this quantitative estimate with simulations.

Description

Keywords

3403 Macromolecular and Materials Chemistry, 34 Chemical Sciences, 51 Physical Sciences

Journal Title

Nat Commun

Conference Name

Journal ISSN

2041-1723
2041-1723

Volume Title

13

Publisher

Springer Science and Business Media LLC