could not initialise potential from xml_label about fox HOT 2 CLOSED

Thanks for the report. From what I can see, the first error (Cannot open second root element (Possibly near line=0 col=949)) should only be generated by FoX when it is asked to read a document that is not XML well formed. Specifically, you should see this for documents which look something like:

<root_node_1>
      <some_more_nodes/>
 </root_node_1>
 <root_node_2>
      <some_more_nodes_or_not/>
 </root_node_2>

This is not permitted so FoX errors out. To check that this is really a problem with the XML file and not a bug in FoX, you could try running the XML file through the xmllint command line tool (usually installed on Linux systems).

The second error looks like a problem in lammps rather than FoX. I wonder if it (or quip) was expecting additional information? But that's something for lammps/quip (which use FoX) I suspect.

from fox.

Oh, I am really sorry. I have realized right now that I have incorrectly opened this issue here. My aim was to post it in QUIP repository. I am closing this, since as you correctly suggested the issue here is on the side of QUIP/LAMMPS. But thanks for the answer anyway.

from fox.