ASE vibrations example

[ajjackson]

Hi,

from ASE version 3.22 there is a VibrationsData object that can be instantiated from Hessian data. It looks like this is very simple to use with TorchANI's analytic Hessian feature:

following the tutorial at
https://aiqm.github.io/torchani/examples/vibration_analysis.html

I can add

from ase.units import Hartree
from ase.vibrations.data import VibrationsData
vibdata = VibrationsData.from_2d(molecule, hessian[0] * Hartree)

print(vibdata.tabulate())

which returns

---------------------
  #    meV     cm^-1
---------------------
  0    0.0i      0.1i
  1    0.0       0.0
  2    0.0       0.0
  3    0.0       0.0
  4    0.0       0.0
  5    0.0       0.1
  6  237.2    1913.2
  7  481.4    3882.4
  8  484.9    3911.2
---------------------
Zero-point energy: 0.602 eV

in agreement with freq. This object provides some other nice features, such as the .write_jmol() and .iter_animated_mode() methods for visualization. Of course, it also makes comparison with finite-displacement vibrations straightforward.

Would it be helpful to open a PR adding some of this to the documentation?

[yueyericardo]

Thanks for sharing the information and the integration idea. We appreciate your suggestion. A PR is welcomed!