.wvfn.nnnn this file contains a record of the wavefunction. The presence of this file allows a secondary restart mechanism. In the param file set
ELEC_RESTORE_FILE
To the root name.
.bands this file contains the electronic eigenvalues related to the individual k-points.
.err.nnnn this is an error file, written by every MPI process. If a job terminates unexpectedly this file will provide a ready source of diagnostic information. nnnn is the MPI rank. A job run in parallel on, say, 4 processors will return up to 4 .err. files depending on which nodes the problem has occured. If the calculation is run in serial without MPI then nnnn = 0001.