The material I'm working has been found in a mixed state of different space groups experimentally. My question is that
1. Can such multi-structural calculation be done in quantum espresso ?
2. If yes, how to include all these structures in one input ?
You can proceed with one type at a time and construct other inputs separately for other types and so on. I think it is impossible to consider all structures in a single input. As to me most stable type is better to choose. You can also do calculations for all types you need
It is possible, but the whole system's size could be very large. This might be applied if you want to build a nanoparticle with several space groups.
We can also choose the dominant crystal structure based on the XRD data. Then, the calculation can be performed using the chosen one. We might expect that the calculated data can approach the experimental data. However, of course, the calculated result could (slightly) deviate from the experimental data.
In our research, we choose the most stable surface structure to simulate oxygen reduction on the surface: Article Effect of Nitrogen Doping and Oxygen Vacancy on the Oxygen R...
.However, for different environments (such as high temperature or high pressure), the most stable structure could be different.
Best regards,
Muhammady
JP
Understanding the polycrystalline material you have synthesized the mixed states would be present in different concentrations in your sample. If you want to simulate the whole mixed-phase structure there are two possibilities.
1) Here you can design structures of all the phases big enough that when they are given a vacuum on three sides they do not convert into clusters, thereafter you can take a large cell and place all these samples and then optimize the whole cell. Although you won't get precise results you will get a similar pattern.
2) Study different phases individually in terms of structural, dynamical, and electronic properties and you will see any specific phase showing good results than others for the synthesized sample the structure with a high concentration of that phase will show similar behavior. Thus you can identify the role of every phase and it will match your experimental results.
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