The link given in the reply was related to the question on how "to make the interface".
For the hole density, I would first calculate Electron density for the three systems: the Diamond (100) - Molybdenum Trioxide, the Diamond (100) surface, and Molybdenum Trioxide, and then computing the difference as described, e.g., in Phys. Rev. B 79, 195425 (2009). The charge transfer can then be computed from the difference, see again the above mentioned paper.