  The effects of the spin and lattice degrees of freedom on the electronic
structure of M1 vanadium dioxide are explored using a quasiparticle
description. Contraction of the inter-vanadium spacing of the Peierls pairings
stabilizes bonding electrons, reducing polarizability and thus widening the
band gap. Increases of this inter-vanadium spacing of as little as 1 \% reduce
this stabilization, resulting in a crossover to ferromagnetic behaviour
accomplished by half of the valence electrons inhabiting the leading edge of
the conduction band in localized atomic-like orbitals, as the antiferromagnetic
order becomes unstable with respect to rearrangement according to Hund's first
rule. The data indicates that the magnetic structure of M1 vanadium dioxide may
be finely balanced; the antiferromagnetic order is a consequence of the
overlapping nuclear potential of the Peierls pairs, and input which disrupts
this will have a significant effect on magnetic properties.
