Cannot read Castep 16.11 bin file

[mducle]

The following is a valid .castep_bin file as far as I can tell, and has the required FORCE_CON field but euphonic gives the following error when trying to read it:

cp-out.castep_bin.zip

>>> fc = ForceConstants.from_castep("cp-out.castep_bin")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\\mambaforge\envs\eu39\lib\site-packages\euphonic\force_constants.py", line 1833, in from_castep
    data = castep.read_interpolation_data(filename)
  File "C:\mambaforge\envs\eu39\lib\site-packages\euphonic\readers\castep.py", line 472, in read_interpolation_data
    cell_origins = np.reshape(
  File "C:\mambaforge\envs\eu39\lib\site-packages\numpy\core\fromnumeric.py", line 285, in reshape
    return _wrapfunc(a, 'reshape', newshape, order=order)
  File "C:\mambaforge\envs\eu39\lib\site-packages\numpy\core\fromnumeric.py", line 56, in _wrapfunc
    return _wrapit(obj, method, *args, **kwds)
  File "C:\mambaforge\envs\eu39\lib\site-packages\numpy\core\fromnumeric.py", line 45, in _wrapit
    result = getattr(asarray(obj), method)(*args, **kwds)
ValueError: cannot reshape array of size 1 into shape (1,3)

The file was generated by Castep 16.11 - possibly there was some change of format of the bin-files between Castep-16 and Castep-19 which was what euphonic was written against.

[krefson]

There was a change in the format of the checkpoint file in 17.1, which would affect the reading by Euphonic. (The field phonon_supercell_origins was added).

There's code in CASTEP to read older versions of the checkpoint file, so the easiest thing to do may be to perform a minimal "continuation" run (Literally just have one line in the param reading "continuation : "; you will need the original .cell file too). Run with the current version and this ought to regenate a checkpoint which Euphonic can read.

[mducle]

If there is demand for this, we could compute the phonon_supercell_origins field in Euphonic. There is already some code in the phonopy reader which could be repurposed for this.