Gaussian-n composite methods

[berquist]

Description

This adds the Gaussian-n (Gaussian-1, Gaussian-2, ...) composite methods for thermochemistry.

What are your new additions? Please provide a brief list.

• New Features

  • G1
  • G2 and G2(MP2)
  • G3 and G3(MP2)
  • G4 and G4(MP2)

• Changes

  • None for existing code.

Any questions for the community?

• Not right now. I think I uncovered a strange or wrong keyword in Psi4's composite code, but I need to check (this was ~2 years ago).

Status

• Click when ready for review-and-merge

[dgasmith]

This is really cool, thank you for starting in on these!

[hokru]

PSI4 has G1/G2 methods. I think they are undocumented? Or at least hidden. Could be useful for comparison.
https://github.com/psi4/psi4/blob/master/psi4/driver/gaussian_n.py
energy('g2')