Hi Mauricio,
Thanks for your report. I can reproduce the 'problem'; it has nothing to do with including $X3DNA/config in the environment settings.
The error message:
open_file <./Atomic.g.pdb> failed: No such file or directory
means 3DNA (find_pair) is trying to locate the file in your current working directory (CWD), instead of the default system setting $X3DNA/config where the file Atomic.g.pdb is available, among other Atomic*.pdb files.
If file Atomic_A.pdb exists in your CWD, 3DNA assumes all other Atomic*.pdb files there as well. That's normally true if you run, e.g.:
x3dna_utils cp_std bdna
For your case, you must have Atomic_A.pdb and possibly several other canonical base Atomic_[CGTU].pdb files in your CWD, but not the modified version (in lower case, prefixed with a dot instead of underscore). So simply run the following command in you CWD will do the trick:
cp -f $X3DNA/config/Atomic.*.pdb .
Alternatively, you can delete all the Atomic*pdb files from your CWD, and find_pair will work as expected:
rm -f Atomic*.pdb
find_pair 1ehz.pdb stdout
Please have a try and report back how it goes.
I may consider to refine 3DNA to check for each Atomic*.pdb file separately, but that would complicate the code. You are actually the first to notice this 'limitation'. Practically, knowing what's happening behind the scene, you can easily work around it, as suggested above.
HTH,
Xiang-Jun