There are quantitative errors in Figs. 1 and 2 of our paper, affecting its first conclusion. Stress evaluation employing the Vienna ab initio simulation package (vasp) on inhomogeneous structures and, in particular, on structures where internal strain occurs, requires special handling. Bilayer graphene is such a structure with a large vacuum separation in the supercell along the c axis perpendicular to the graphene plane. We misinterpreted the stress presented in the original Fig. 1 as the stress on the graphene layers. We correct the stress in Fig. 1 below by a simple scaling following the approach in the literature [1,2]. The key message is qualitatively consistent with the original paper, that bilayer graphene stiffens more slowly than graphite over the compression range before the rehybridization of s p 2 to s p 3 (i.e., the curve of the stress against the interlayer spacing of the bilayer is shallower than graphite in this range). Additionally, a systematic error in integrating the charge density influenced the discussion of the charge between graphene layers. This error is corrected in Fig. 2, and its impact is discussed in the corresponding text below. Despite the errors arising from these methodological mishandlings, the original interpretation and conclusions remain qualitatively unchanged.