Q. My run aborted with a message of the type Error XXXX: Failed to open YYYY
A. This is an I/O failure reported when CASTEP attempts to read an input file which does not exist or does not have read permission. Check your input files and directory permissions carefully.
Q. ''wave_orthonormalise_overlap_wv_ks: ztrtri failed in inversion'
A. This error literally means the overlap of a wavefunction with itself cannot be inverted, a procedure which is necessary in order to ensure the wavefunction's bands are orthogonal (obey the Pauli exclusion principle) and normalised (contain only 1 particle each).
The error can arise for a number of different reasons but the most common is that some atoms are extremely close to each other (closer than the sum of their pseudopotential core radii). You should check your input geometry and make sure the atoms are not too close; if you really want the atoms to be this close then you may need to generate new pseudopotentials with smaller core radii.
A. This message means that an I/O failure occurred while attempting to write wavefunctions to a file - usually the checkpoint file. The most likely cause is a disk full or quota exceeded. If this occurs, the checkpoint file in question will be truncated and corrupted - see the following answer.
A. This specific I/O failure is usually the result of attempting to read a corrupt or incomplete checkpoint file. If can also occur during phonon calculations reading the
.fd_wvfn files, which contain supercell ground state wavefunctions. In each case the cause is probably that the prior run which wrote the file in question being killed during the write operation, or the disk quota being exceeded. The only remedy is to delete the checkpoint file in question.
Note that there may be an intact
.check_bak file which is usable.