A Question about defect concentrations

One of you sent me the following email:

    I’m trying to follow your book, to get through these homework questions, and one problem I’m frequently having is with notation.  I am not certain which notation is used for mole fraction, atom percent, concentration, or just number when talking about a specific type of defect in crystals.  To compound the matter, we are learning about these defects in thermo as well, and while they use the Kroger vink notation as well, I’m having a lot of difficulty following.  Can you consolidate, or simplify this problem for me?

Answer:

It is not that complicated; when you see square brackets that is a mole FRACTION and dimensionless.  If you see something like Vo, n or p, WITHOUT brackets then that is usually either per mole or per m3 depending on the problem.  When dealing with conductivity then you HAVE to use number of defects per m3.  Michel