Density functional theory analysis of flexural modes, elastic constants, and corrugations in strained graphene

TL;DR

This study uses density functional theory to analyze how flexural modes, elastic constants, and atomic corrugations in strained graphene are affected by stress, revealing their roles in rippling and thermal behavior.

Contribution

It provides a detailed ab initio analysis of flexural modes and corrugations in graphene under stress, linking vibrational properties to mechanical and thermal phenomena.

Findings

Flexural mode frequencies are sensitive to compressive stress.

Under compression, rippling amplitudes increase significantly.

Flexural modes contribute to large atomic corrugations and instability.

Abstract

Ab initio density functional theory has been used to analyze flexural modes, elastic constants, and atomic corrugations on single and bi-layer graphene. Frequencies of flexural modes are sensitive to compressive stress; its variation under stress can be related to the anomalous thermal expansion via a simple model based in classical Elasticity Theory [Phys. Rev. B 86, 144103]. Under compression, flexural modes are responsible for a long wavelength rippling with a large amplitude and a marked anharmonic behavior. This is compared with corrugations created by thermal fluctuations and the adsorption of a light impurity (hydrogen). Typical values for the later are in the sub-Angstrom regime, while maximum corrugations associated to bending modes quickly increase up to a few Angstroms under a compressive stress, due to the intrinsic instability of flexural modes