Add the option to change the probability of the atom type occurence

[gasevic]

I noticed that many structures include e.g. B or Al since they lead to stable structures. Therefore, it would be helpful to change the probability of their occurrence. This could, e.g, be done in a similar way as element_composition by setting the probability to 100% for every atom type and letting the user set custom probabilities in the .toml file:

element_probability = "Al:0.5,B:0.3"

[marcelmbn]

After our in-person discussion, I spent some thoughts on this, and one way to implement this (while still being in accordance with the basic working principle of the code and not cluttering it too much) would be the following:

• Initializing an array of len(103) filled with 1.0 for each
• User input similar to the one for element_composition would enable manipulating these values for specific elements. Values > 1.0 would increase the probability of this element being chosen, while values < 1.0 would decrease it.
• For the part, in which random atoms are assigned for the atom list (of the resulting molecule) (and only for that part!), an integer element number ranging from 1 to 103 (or currently 86) would not be chosen completely randomly but weighted by the aforementioned array. This is probably super easy to realize using numpy.

What do you think about these ideas, @gasevic? And maybe pinging also @jonathan-schoeps?

[gasevic]

Sounds good to me!