Dear Paola

I am learning how to use Yambo through the online tutorials ("Fantastic dimensions"), and I am using Pwscf for the initial calculations.

Welcome and thank you for your interest in yambo.

In the very first initialization step, Yambo reads how many G-vectors were used by the previous program to develop the wavefunctions and writes the actual number that it will use.

In this first step, all three numbers you are referring to are read and stored in (n)s.db1. You should have these 3 lines (with different number of course) in the standard output of the p2y run

- Code: Select all
`<---> :: Max WF components : 8749`

<---> :: RL vectors (WF): 8749

<---> :: RL vectors (CHARGE): 8749

In the initialization outputs shown in the tutorials, I've noticed that the keywords G-vectors, Components and WF G-vectors in the section "[RD./SAVE//s.db1]" are always equal. This is not my case, though, when I try to do again the exercises of the tutorial: the values of Components and WF G-vectors are the same, but they are smaller than the value of the G-vectors

At hte beginning of every run then, the files created by the interface (s.db1 and s.wf) are read. In the report under [RD./SAVE//s.db1] you have all the parameters that are read (RD) by yambo from s.db1 in the dir SAVE. So the three numbers G-vectors, Components and WF G-vectors are the same as those read above. In particular Max WF components corresponds to Components, RL vectors (WF) corresponds to WF G-vectors (RL stays for reciprocal lattice, those vectors are standardly indicated with the letter G), and RL vectors (CHARGE) corresponds to G-vectors.

I would like to know:

1) what do these keywords exactly refer to?

2) do they have to be always equal or not?

2) No they can be equal, but they do not need to. In particular G-vectors >= WF G-vectors >= Components

1) G-vectors is the maximum number of vectors used in the dft code. This can be larger than the number of reciprocal vectors used to describe the wavefunction (WF), e.g. to calculate the charge density. The other two numbers corresponds to the G vectors for the wavefunctions.In particular Components gives the maximum number of G vectors used to describe the wavefunction in reciprocal space (maximum because the number can change depending on k vector).WF G-vectors is used to handle the way of indexing the component in PWscf. (In fact when using the WF from other dft code eg. Abinit Components is set = WF G-vectors).

I hope this help you. Have fun with the tutorials!

Regards,

Myrta