Yambo Community Forum

Dear all

I would like to use the yambo code to calculate the optimized geometry of several excited states of isolated molecules.
Does someone know if the code is able to solve this type of problems? Are there input examples ?
Does or will the code perform relaxation ?
Can i calculate emission spectrum using yambo ?

Best Regards
Martin

Dear Martin,
Unfortunately Yambo does not perform this kind of calculations. At the moment any ionic relaxation (or dynamic in general) is implemented.
Emission spectra can be calculated, but the geometry has to be provided.
Have a look to the features and tutorials pages to see what yambo can do.
Best,
Daniele

Dear Daniele,

At the moment any ionic relaxation (or dynamic in general) is implemented

How can i do this? I could not find any thing regarding relaxation !

Emission spectra can be calculated, but the geometry has to be provided

I can provide the optimized geometry in the excited state but again i could not find any tutorial describing how to carry out an emission spectrum calculation (photoluminescence).
I see only absorption spectrum calculations.


For electron phonon coupling should i add these patches at the end of the tutorial to quantum espresso or these patches are already there in the new version of QE ?

Regards
Martin

Dear Martin,
1) relaxation: it depends on what system and what theory you want to use.
For molecules there are different codes that do that work at TDDFT level in gaussian basis set.
At MBPT level I only know few works of the S. Louie group: see e.g. Phys. Rev. Lett. 90, 076401, of some years ago, but I do not know if it is implemented in some code, surely currently not in yambo.

2) If you have the excited state geometry then emission and absorption are equivalent, the difficult task is to find a reliable excited state geometry (see point 1). Sorry, but I cannot understand your point 1, if you say that you can provide such geometries.

3) As reported here:
The way Yambo computs e-p interaction is too complicated at the moment due to the fact that the interface with QE is out-of-date. We are working on this and in the new release of Yambo the e-p interaction should be fully working.

Best,
Daniele

Dear Daniele,

1) I am interested in geometry optimization within MBPT but as you said this is currently not implemented in yambo.

2) I meant, i can calculate excited state geometries within the framework of restricted and unrestricted Hartree Fock theory and use it.
yes, for molecules absorption and emission in gas phase should be the same but not for solids (there should be a shift).

3) So there is right now only problems with the interface to QE but yambo_ph is okay ?

Regards
Martin

Dear Martin,
I'm not totally aware about the status of the code about e-ph, yes the problem is the interface.
As well as performing GW calculations starting from hybrids. People involved in that will give you an answer soon. About self-consistency, it is partially implemented in yambo, not in gpl version, and I hope it will be released soon.

Best,
Daniele

Dear Martin,

martinspenke wrote: 1) I am interested in geometry optimization within MBPT but as you said this is currently not implemented in yambo.

This is a quite advanced and complicated issue. I fear I do not even know hot such a geometry optmiziation can be done by using MBPT without adopting some crude approximations as done, for example, in an old paper of Steven Louie about self-trapping phenomena.

martinspenke wrote: 2) I meant, i can calculate excited state geometries within the framework of restricted and unrestricted Hartree Fock theory and use it.
yes, for molecules absorption and emission in gas phase should be the same but not for solids (there should be a shift).

Ok. This sounds ok to me. But in solids HF is a too crude approximation and, moreover, the excited state approximated with a restricted occupation distribution could not well represent the experimental excitation.

martinspenke wrote: 3) So there is right now only problems with the interface to QE but yambo_ph is okay ?

I am working on implementing in the latest QE source the QE to Yambo electron-phonon interface. But I do it in my spare time as there are many things in Yambo to do at the moment. I do hope to release it in the next months.