  Vanadium dioxide undergoes a first order metal-insulator transition at 340 K.
In this work, we develop and carry out state of the art linear scaling DFT
calculations refined with non-local dynamical mean-field theory. We identify a
complex mechanism, a Peierls-assisted orbital selection Mott instability, which
is responsible for the insulating M$_1$ phase, and furthermore survives a
moderate degree of disorder.
