def freq(atoms=None):
if atoms is None:
atoms = read('md.traj',index=0)
atoms.calc = IRFF(atoms=atoms,libfile='ffield.json',rcut=None,nn=True,massage=2)
# Compute frequencies
frequencies = Vibrations(atoms, name='freq')
frequencies.run()
# Print a summary
frequencies.summary()
frequencies.write_dos()
# Write jmol file if requested
# if write_jmol:
frequencies.write_jmol()
