More efficient thermo function

[Andrew-S-Rosen]

Summary of Changes

Get just the point group data in the thermo function.

Checklist

• I have read the "Guidelines" section of the contributing guide. Don't lie! 😉
• My PR is on a custom branch and is not named main.
• I have added relevant, comprehensive unit tests.

Notes

• Your PR will likely not be merged without proper and thorough tests.
• If you are an external contributor, you will see a comment from @buildbot-princeton. This is solely for the maintainers.
• When your code is ready for review, ping one of the active maintainers.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.13%. Comparing base (109c993) to head (a17f8f1).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2021   +/-   ##
=======================================
  Coverage   99.13%   99.13%           
=======================================
  Files          81       81           
  Lines        3336     3338    +2     
=======================================
+ Hits         3307     3309    +2     
  Misses         29       29           

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