NMA periodic systems

[chr...@lehigh.edu]

Hello,

I'm testing TAMkin on a periodic methane molecule who's structure has been relaxed using VASP/5.4.1 (corresponding CONTCAR and OUTCAR attached).

My goal is to generate the molecular partition function based on the contributions from the electronic, translational, rotational, and vibrational partition functions. Specifically, I would like to obtain frequencies corresponding to the rotational, vibrational and translational modes.

Unfortunately I have come across this error: (script attached)

Traceback (most recent call last):

  File "thermo.py", line 14, in <module>

    pf = PartFun(nma, [ExtTrans(), ExtRot()])

  File "/share/Apps/py-ase/opt/spack/linux-centos7-x86_64/miniconda2/4.3.14-ut2miar/gcc-6.1.0/lib/python2.7/site-packages/tamkin/partf.py", line 1353, in __init__

    term.init_part_fun(nma, self)

  File "/share/Apps/py-ase/opt/spack/linux-centos7-x86_64/miniconda2/4.3.14-ut2miar/gcc-6.1.0/lib/python2.7/site-packages/tamkin/partf.py", line 1006, in init_part_fun

    raise ValueError("There is no external rotation in periodic systems.")

ValueError: rotational: There is no external rotation in periodic systems.

Thank you,

Chris Rzepa