▎ 摘　　要

We address the stability of the surface phases that occur on the C side of 3C-SiC((1) over bar(1) over bar(1) over bar) at the onset of graphene formation. In this growth range, experimental reports reveal a coexistence of several surface phases. This coexistence can be explained by a Si-rich model for the unknown (3 x 3) reconstruction, the known (2 x 2)(C) adatom phase, and the graphene-covered (2 x 2)(C) phase. By constructing an ab initio surface phase diagram using a van der Waals corrected density functional, we show that the formation of a well defined interface structure like the "buffer layer" on the Si side is blocked by Si-rich surface reconstructions.