Purification of 2-body DMs

[ghb24]

Thanks for the nice code.

We've been playing around a bit with implementing some algorithms to purify a given 2-body reduced density matrices to make them (approximately) N-representable, initially based on the work of https://doi.org/10.1063/1.4994618 that I know some of the PyCI developers were involved in.

I'm aware that related algorithms for this purpose are an undocumented feature of the PyCI code, and was wondering whether they are a) functionally complete [the P and Q conditions don't seem to be implemented? We would be happy to add them], b) whether you are happy for them to be used, c) whether you can provide a simple example to be sure that we are using the code correctly or any caveats you want to mention on its limitations or effective use?

Many thanks,
George

[PaulWAyers]

Hi George,

We started to implement new (better) algorithms for this last Winter and as an undergrad project over the summer, but didn't finish. I'll talk to @RichRick1 and we can see what our situation is. I think our new code should work for P, Q, G, and maybe T2; honestly it's been too long. We'd intended to write a paper or two on the better refinement but too many things this year.

Take care,

--Paul.

[ghb24]

Hi Paul,

Good to hear from you, and thanks for the response. It doesn't appear as though the code is complete, but found it looking for some comparisons to our own purification implementations we've started working on. Happy to work together on some of these ideas to complete the code if interested, as its a useful tool and something we need in another project.

Best,
George