Question about EBCC

[Physfock]

Could you provide more examples for calculations with electron-boson coupled clusters? I am interested in learning how to define the coupling vector λ and Ω_cav within your format, as shown in the example:

nbos = 5
nmo = mf.mo_occ.size
g = np.random.random((nbos, nmo, nmo)) * 0.03
omega = np.random.random((nbos,)) * 5.0

In particular, I am interested in the format of the paper https://arxiv.org/pdf/2310.02100 (see Fig. 1(d) therein). Where can I also learn about EBCCSD and how to use it within your implementation?

[obackhouse]

Sorry for the delay, I was hoping to find time to dig into this in more detail but might be a bit later in the week, so for now:

The best place to look is the example 01-ebccsd.py, which explains the notation. It looks like the paper you link uses, in my notation, an operator that corresponds to CCSD-S-2-1 (eqn 6), which I don't currently support but could conceivably add without too much hassle.

In brief, the g matrix is (at least closely related to) the coupling (lambda in the paper), and \omega are the bosonic frequencies, also \omega in the paper. I'll try to get around to digging into this in more detail this week and see if I can reproduce the results in some way.