CCSD (+ others) via Tensor Contraction

[jarvist]

Intent is to use -> https://github.com/Jutho/TensorOperations.jl

An interesting approximate algorithm here: https://arxiv.org/abs/1708.02674

The granddaddy is the TCE, as used in NWCHEM: http://www.csc.lsu.edu/~gb/TCE/ https://doi.org/10.1080/00268970500275780

• it's a DSL written for tensor operations - so something that should be relatively easy to implement in Julia, and then quite fast with the . dot splatting.