VW  CVM 1.1 
We can reuse all the isometry notation from the rectangular cell . Now the translation h, formerly viewed as a horizontal translation, is actually the diagonal translation halfway into the new cell, though we still call it h. A new player is M_{x}, the reflection about the xaxis, which is the central axis of the new cell; M_{v} and the As and Bs are as before.
The rhombic lattice cell 
The general term in the sum is the same as that for the rectangular cell,
but now we have the requirement that

