Extended Data Fig. 3: Bubble approximation in the static limit of the SCHA theory.
From: Bending rigidity, sound propagation and ripples in flat graphene

(a) Physical phonons in the static approach with the atomistic potential at 500 K including and neglecting \(\mathop{{{{\boldsymbol{\Phi }}}}}\limits^{(4)}\) in Eq. (11). (b) panel only includes the ZA modes and it is in logarithmic scale. The calculation is done in a 6 × 6 supercell.