I've got a problem with the number of licenses for CASTEP en Mat Stud. We reach the limit (21) with just a few students running in parallel. We have an academic licence (Bronze). What can we do?

Checking, I realized that the same problem happens with DMol. It takes one licence each 4 cores. It means that a 24 multicore processor needs 6 licenses. 

Could you please provide a solution? Thank you.