Maejo International Journal of Science and Technology (Mar 2010)
Crossing points in the electronic band structure of vanadium oxide
Abstract
The electronic band structures of several models of vanadium oxide are calculated. In the models 1-3, every vanadium atom is connected to 4 oxygen atoms and every oxygen atom is connected to 4 vanadium atoms. In model 1, a=b=c 2.3574 Å; in model 2, a= 4.7148 Å, b= 2.3574 Å and c= 2.3574 Å; and in model 3, a= 4.7148 Å, b= 2.3574 Å and c= 4.7148 Å. In the models 4-6, every vanadium atom is connected to 4 oxygen atoms and every oxygen atom is connected to 2 vanadium atoms. In model 4, a=b= 4.551 Å and c= 2.851 Å; in model 5, a=b=c= 3.468 Å; and in model 6, a=b=c= 3.171 Å. We have searched for a crossing point in the band structure of all the models. In model 1 there is a point at which five bands appear to meet but the gap is 7.3 meV. In model 2 there is a crossing point between G and F points and there is a point between F and Q with the gap ≈ 3.6608 meV. In model 3, the gap is very small, ~ 10-5 eV. In model 4, the gap is 5.25 meV. In model 5, the gap between Z and G points is 2.035 meV, and in model 6 the gap at Z point is 4.3175 meV. The crossing point in model 2 looks like one line is bent so that the supersymmetry is broken. When pseudopotentials are replaced by a full band calculation, the crossing point changes into a gap of 2.72 x 10-4 eV.
