Author Topic: SQS Alloy  (Read 133 times)

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Offline quanta

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SQS Alloy
« on: May 16, 2021, 20:11 »
Hello,

Can you help me to use SQS alloy in the builder? Is there any guide to know the parameter that is used to create alloy? Also, How do I know the latest result is the best structure? What is the meaning of corelation function error? Does it need to be close to zero? Thank you.

Offline Petr Khomyakov

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Re: SQS Alloy
« Reply #1 on: May 17, 2021, 13:57 »
The theory of SQS and guidelines for generating these structures are given in this papers A. Zunger, S.-H. Wei, L. Ferreira, J.E. Bernard, Special quasirandom structures, Phys. Rev. Lett. 65 (3) (1990) 353; S.-H. Wei, L. G. Ferreira, James E. Bernard, and Alex Zunger, Phys. Rev. B 42, 9622 (1990), see also https://docs.quantumatk.com/manual/Types/EvolutionarySQS/EvolutionarySQS.html.

As a general guideline, increasing accuracy of SQS requires larger supercells, higher Max Expansion Order (the current default is likely good enough so), using larger number of generations, using the largest possible cluster diameter, see a png-file enclosed. The goal is to get error for correlation functions as small as possible for a given expansion order and max cluster diameters (default is likely good enough).  Note that setting very strict parameters might lead to significant increase of computational time. Again, quality of SQS is quantified in terms of correlation function errors.

Offline quanta

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Re: SQS Alloy
« Reply #2 on: May 20, 2021, 22:57 »
Thank you so much for quick and great answer