Hi all..

I would like to use Vanadium 2+ and 3+ in my cathode material simulate using castep. However im confusing how i gonna state the oxidation number of the vanadium. There are several ways that im thinking

1. Change the oxidation state at the properteis of the atom
2. Change the change at the properties 
3. change the formal charge.

my question is which is the right way to represent the oxidation number of the vandium in CASTEP simulation.

Thanks you very much