Figure 3: Calculation of phonon modes in nanometre-size graphene dots.

(a) Schematic of graphene dot of diameter d, wherein the atoms inside the dot are free to move while those outside are stationary. (b) Graph of cumulative phonon density of states (DOS) for graphene dots with different diameters. All graphs are normalized so that the maximum cumulative phonon density of state (CDOS) is 1. (c) Projection of each phonon mode to a plane wave with momentum K and out-of-plane displacements for graphene dots with d=1, 2 and 6 nm. (d) Root mean square (r.m.s.) amplitudes of the phonon modes with K projections larger than one-third of the maximum K projection for the d values shown in c.