# Tag Info

10

Often we are hung up on the idea of making sure we generate an SQS of a size (i.e. # of atoms) that matches the composition of our system. For instance, in the case of $A_3B$ we would generally take multiples of 4 as the # of atoms. This isn't always enough, especially in your case. Since you want to make a cell that is ordered in certain layers and ...

10

First of all, it's better to define the terms here because probably not all the people here are familiar with SQS right away. SQS is an abbreviation for special quasirandom structures. The illuminating reference here is the work of Zunger et. al. that basically show you that the most relevant parameter to consider when you want if SQS truly resembles a ...

4

These are some general comments about modelling disorder which I think address your question, but note I cannot provide specifics about the codes you are using. Imagine a simple configuration with only two sites for the discussion: Both atoms are of the same type (blue) so that this configuration has a mirror plane down the middle of the two atoms (dashed ...

4

There are a number of open-source and commercial software that can do a completely random substitution alloy. In the open-source segment, you can try the python software: Pymatgen (https://pymatgen.org/). Atomsk (https://atomsk.univ-lille.fr/) is another great software to do this. I have tried to do this using Atomsk and it works perfectly. In the commercial ...

3

There are two different perspectives here. The first one is the creation of the SQS structure itself accomplished through the ATAT package, for example. The second one is the calculation of the slab properties. The SQS procedure returns the smaller structure that resembles the periodic structure properties. For alloys, for instance, the inputs are the ...

2

Caution: Self answer ahead! Let's understand it with an example of a binary $AB$ compound. A correlation function for a particular type of cluster (pair, triangle, tetrahedron, etc.), $\rho$, is defined as \begin{equation} \rho_\alpha\: =\: <cluster function>_\alpha,\tag{1} \end{equation} Where $\alpha$ represents the type of cluster and $<...>$ ...

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As Anibal points in his answer, generating the SQS and using it for a surface calculation are two separate things, and shouldn't affect each other. You would still take all precautions as usual while performing the DFT calculation. That being said, there could be scenarios where you may want to restrict/prefer certain atom types amassing at edges or corners ...

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