  First-principles approach is demonstrated to calculate the work function of
Bi2Te3. The reference potential and the vacuum energy levels are extracted from
the Bi2Te3 (0001) surface structure using the reference potential method based
on the density functional theory. The one-shot GOWO many-body perturbation
theory is used to place the bulk band edge energies with respect to the
reference level and the vacuum energy. At last, the work function of 5.301 -
5.131 eV is predicted for Bi2Te3 (0001) surface and compared to various
elements.
