Meaning of the coupled cluster amplitudes

[jmisiewicz]

Quoting myself from another topic:

Understanding MP2/CCSD amplitudes for H4

T_IJAB and T_ijab are excluded from Psi’s RHF MP2/CCSD codes (as well as most other production-level codes for doubles theories) because they’re not necessary. While I couldn’t give you the derivation of the rule, the result is that T_IJAB = T_IjAb - T_IjBa = T_ijab. Psi’s RHF implementation of these methods invokes these equations throughout, so that only the ABAB spin case is required.

This is a very old topic, so unless you have a follow-up, I’m going to lock this topic and invite further discussion to go into a new topic.