8.6 How do I play with the compositions?

For variable-composition and single block calculations, as soon as the calculation starts, it produces a file Seeds/compositions with all possible compositions, from which the code randomly takes compositions for the random structure generator. You can edit this file, leaving the compositions you are most interested in — only these compositions will be used for random structure production in the second and subsequent generations. Seeds/compositions file lists the numbers of atoms of each type in the cell, e.g., for the C-O system:

    8 0
    0 8
    2 4

means that you are interested in randomly producing C, O, and CO structures. Other compositions will be sampled too, thanks to the heredity and transmutation operators.

When you want to generate structures with specific compositions, you can use the anti-compositions feature — write the list of all unwanted compositions to the file named Seeds/Anti-compositions. There are three ways to do so:

1. For all unwanted compositions with the same ratios, you can write stoichiometric ratio to ban these compositions. For example, you can use “1 2 1” to ban all the composition with the same ratio, such as “1 2 1”, “2 4 2”, “3 6 3” and so on.

2. Only for the specific composition, but not for other compositions with the same ratio. You can write the compositions with a minus sign. For example, you can use “-3 2 0” or “3 -2 0” to ban the “3 2 0” composition, but not to ban “6 4 0” or “9 6 0” composition. (Notice: “3 2 -0” does not work for this case).

3. For all single/binary/ternary compounds. If you don’t want to sample all single/binary/ternary compounds, just write the keyword single/binary/ternary in Anti-compositions file.

Example:

    single
    binary
    1 1 2
   -2 2 1

If you don’t clearly know what you are doing, please leave Anti-compositions file empty. For more information about the compositions you don’t want, you can have a look at results1/compositionStatistic file.

NOTE:

• Even if compositions or Anti-compositions files exist before the calculation starts, they will be ignored. Anti-compositions file will be renamed to a backup file Anti-compositions-back. Therefore, please edit compositions or Anti-compositions files after the calculation starts.

• Please also be aware, that in USPEX calculations with compositional blocks, the compositions usually mean the numbers of these blocks. Therefore, to have the correct format of Anti-compositions file, please check compositions file first.