When running a cell relaxation, it is sometimes nice to monitor what is going on with the cell parameters. If you run the cell relaxation with Quantum Espresso, you can use my python script “pw2cellvec” to parse all the information you need.
So, first of all, run a “vc-relax” calcuculation with a large (about 2 times bigger) cutoff for both wavefunction (ecutwfc) and charge (ecutrho) and wait for a couple of iterations. These calculations are very expensive, due to the large cutoffs.
Then, just run the script and you will get something like this: