interface with WannierBerri

[stepan-tsirkin]

Dear developers

@AntimoMarrazzo brought my attention to this package. From a quick look I am trying to understand what you are trying to do here

strawberrypy/strawberrypy/_wberri/attribute.py

Lines 58 to 65 in 00f646a

	print('Reading Hamiltonian at Gamma point in Wannier gauge..')
	grid = Grid(model, NK=model.NKFFT_recommended)
	dK = 1. / grid.div
	data = Data_K_R(model, dK, grid)
	Ham_W_R = model.Ham_R.copy()
	Ham_W_k = data.fft_R_to_k(Ham_W_R, hermitean=True)
	ham = Ham_W_k[0,:,:]

I guess, you what to get the Gamma-point only, right? Then, computing a grid of size NK=model.NKFFT_recommended is an overhead. instead you may use NK=[1,1,1], dK=[0,0,0]

Why are you using dK = 1. / grid.div ? Well, in this case grid.div should be [1,1,1], and dK is defined modulo 1, so it is equivalent to [0,0,0], so in the end your implementation should work. but it looks unnecessary sophisticated.

Am I understanding correctly, or do you have smth different in mind?

[roberta-favata]

Dear Stepan,
you understand correctly, we want to get the Gamma-point only.
I agree with your suggestion and I will implement it, thank you!