Add the additional triples term when the field is on.

[zw0930]

Description

Add the missing term in the triples equation when the field is on.

Todos

Notable points that this PR has either accomplished or will accomplish.

• Add a method in cctriples to calculate the full set of triples.
• Modify the cc_pert functions and add the additional term.
• Modify ccwfn, cclambda, and ccdensity to calculate the full set of triples and the additional two terms only when the field is on.
• Add GPU version of the code.
• Clean up comments and commented out lines for testing.
• Test the modification.

Questions

• Question1

Status

• Ready to go

[lothian]

What's the status of this PR, Zhe?