  The electronic band structures of two-dimensional materials are significantly
different from those of their bulk counterparts, due to quantum confinement and
strong modifications of electronic screening. An accurate determination of
electronic states is a prerequisite to design electronic or optoelectronic
applications of two-dimensional materials, however, most of the theoretical
methods we have available to compute band gaps are either inaccurate,
computationally expensive, or only applicable to bulk systems. Here we show
that reliable band structures of nanostructured systems can now be efficiently
calculated using density-functional theory with the local modified
Becke-Johnson exchange-correlation functional that we recently proposed. After
re-optimizing the parameters of this functional specifically for
two-dimensional materials, we show, for a test set of almost 300 systems, that
the obtained band gaps are of comparable quality as those obtained using the
best hybrid functionals, but at a very reduced computational cost. These
results open the way for accurate high-throughput studies of band-structures of
two-dimensional materials and for the study of van der Waals heterostructures
with large unit cells.
