I'd like to investigate the structural relaxations of the excited state for periodic systems. It seems BSE is a practical method that has already been implemented in many codes for static calculations.

I'm wondering if there's any code with extensions to force evaluations?

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    $\begingroup$ +1. Welcome to our site! Thanks for asking your question here, and we hope to see much more of you!!! The answer by ProfM is only for BSE. I think this question might be better off being two separate questions, one for TDDFT and one for BSE. We can see what the community feels. $\endgroup$ Sep 8 '20 at 16:30
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    $\begingroup$ I agree with Nike. I think if you split the question in two and provide a link between the two, you will get better answers that more specifically address each method (not to say that ProfM hasn't already provided a great answer for BSE). Since this question already has a BSE answer, I would suggest cutting TDDFT from this question and making a new post for that. $\endgroup$
    – Tyberius
    Sep 8 '20 at 17:29
  • $\begingroup$ About the structure of this question, there is now a discussion on Meta: mattermodeling.meta.stackexchange.com/a/194/5 $\endgroup$ Sep 8 '20 at 17:56
  • $\begingroup$ Thanks. I have split the questions in two parts. The TDDFT part is here mattermodeling.stackexchange.com/questions/2226/…. $\endgroup$ Sep 8 '20 at 21:37
  • $\begingroup$ ABINIT, Yambo and exciting should have BSE. I'm not sure if they have it implemented for the property you want, but they may be a good place to start (or someone with more knowledge of these codes can step in and clarify). $\endgroup$
    – LukasK
    Sep 9 '20 at 11:37

I am not aware of any public codes that have a force implementation for excited state calculations using the Bethe-Salpeter equation (happy to be corrected on this front). However, the methodology to do this was published some time ago by Ismail-Beige and Louie in this paper, where they also have an in-house implementation that they use to validate the methodology by studying:

photoexcited carbon dioxide and ammonia molecules, and the calculations accurately describe the excitation energies and photoinduced structural deformations

  • $\begingroup$ +1. For the fast answer. Maybe this can become HNQ. I suppose the user can get the code from the authors of that paper if they need to do force with BSE. $\endgroup$ Sep 8 '20 at 16:31

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