Theoretical investigation of the electronic and structural nature of thirteen-atom binary metal cluster of AgnBi13-n
Detalhes
- Tipo de apresentação: Apresentação de Pôster / Poster Communications
- Eixo temático: Química Computacional
- Palavras chaves: DFT; nanoclusters; Alloys;
- 1 Universidade Estadual de Campinas
- 2 Venezuelan Institute for Scientific Research
Theoretical investigation of the electronic and structural nature of thirteen-atom binary metal cluster of AgnBi13-n
Manoel Victor Frutuoso Barrionuevo
Universidade Estadual de Campinas
Resumo
1) Bismuth is known to be immiscible with silver. However, recently Longo and coworkers found a way to synthesize AgBi nanoparticles by employing femtosecond laser pulse techniques. Since their work presented the possible use of this new material as a potential antimicrobial, it became interesting from a theoretical perspective to understand the electronic and structural properties of those materials;
2) Herein, we presented a theoretical investigation of AgnBi13-n as a binary metal alloy in which the Ag content is increased one atom at a time to understand how the Ag content influence the electronic structure of the nanocluster system as well as its structural deformation;
3) We have found that going from Ag pure nanocluster adding Bi is highly difficult, as shown by a no significant decrease of the excess energy. On the other hand, adding Ag to a Bi pure nanocluster there is a more effective stabilization of the system's excess energy, which agrees with Longo's finding of low bismuth miscibility into silver's systems;
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Manoel Victor Frutuoso Barrionuevo
Hello Breno, sorry for the late reply, I'm currently working in a different timezone. By the way, thanks for the compliments.
About your question, actually, everything started from a pure cuboctahedral silver structure, as pointed out in slide two. You see, after creating each pool of homotopes by taking into account all atomic permutations possible for a given formula, we optimized each structure until it reaches its minimum energy. Therefore, deformations will occur along with the optimization procedure as the employed DFT model will try to relax all the forces within the structure, changing its symmetry and moving everything around.
Given each homotope from within a group, we managed to get all minimized structures to their local minima. The discussion about "is it a local or global minimum" is a very heated one. Some authors do disagree that by using only a quantum chemical relaxation method one can find the true minimum, others don't think any further. Therefore, I took care of using that language formality saying that we actually found a local minimum, because despite performing hessian calculations for each optimized structure and not finding any imaginary frequency, I have no further data that points me that actually I truly sampled all the energy landscape for that particular structure. Sometimes by performing metadynamics employing DFT one can find an even deeper energy well from that previously found for an already optimized structure. So, I hope my explanation helped you in understanding that.
Please, let me know if you still have any doubts. I'll be glad to answer them all. Take care and have a wonderful congress.
Bye. :)
BRENO RODRIGUES LAMAGHERE GALVAO
Thanks Manoel.
Yes, global optimization is terrible problem, I no one can guarantee to have found the global minimum. That is completely normal.
My question was just to try to understand what you did. If you locally optimized all homotops, you problably did thousands of calculations!
Manoel Victor Frutuoso Barrionuevo
Exactly it Breno.
I did thousands of calculations indeed, well not me actually. It was the computer's task, so with a bit of programming skills, one can manage to do wonders nowadays.
By the way, just for the sake of completeness, all calculations were performed employing CP2K, which by the way I can't stress enough how great it is. I'll always recommend that to everybody. I've been fooling around with Orca, which also is a great tool, but somehow can be a little problematic for those kinds of systems. Sure thing, not impossible to deal with, just a bit cumbersome sometimes. At the end of the day, I guess it is more of a personal choice to which set of programs one is going to use. One might figure out if that program will be capable of performing what is supposed to be done. Otherwise, one can seek for creating its own alternative program. It's always an incredible adventure.
Thanks for your question, I'm truly delighted to get back from you. Have a great one. :)