To further rule out a significant sp 3 -type Gr activation at liquid Cu, we characterize the bonded state of Gr on liquid and solid Cu(111) by analyzing the Gr geometry during the MD simulations at 1200 K. Specifically, we evaluate the distribution of the average differential bond angles of coordinating C atoms 𝛿𝜃 for all the C atoms inside Gr for free-standing Gr and Gr adsorbed on solid and liquid Cu. As a prior for the local coordination environment, values of 𝛿𝜃 of 0° and ± 10.5° represent sp 2 -or sp 3 -hybridized C, respectively. Negative values indicate a C "bending" towards the Cu surface, and positive values a C "bending" away from the surface. As shown in Figure (and Figure for liquid Cu at the even more elevated temperature of 1370K ), the angle distributions are essentially identical for Gr at liquid and solid Cu. This confirms the above conclusion of an absence of additional sp 3 -activation at the liquid metal surface. In fact, there is no significant sp 3 -type hybridization at either surface, as clearly revealed from the absence of any peak at 𝛿𝜃 = ±10.5°. Instead, in particular the difference to free-standing Gr shown in Figure demonstrates that the primary effect of the surface (regardless of whether solid or liquid) at this elevated temperature is to slightly modify the intrinsic longer-range rippling of Gr as reflected by the additional broadening of the angle distribution around 𝛿𝜃 = 0°.