Order of Coordinates

[mmg016]

Dear VNL developers and users,

I have a question regarding the export of a molecular system, For e.g., as a POSCAR. Every time I export a structure, VNL writes the atom coordinates in a completely random order, Even though if we look at the 'coordinate list' in 'Coordinate Tools', atoms are very nicely ordered, like Ni1, Ni2, Ni3.........

I would like to export the file in the same order in which it is listed in 'Coordinate List'. This way I can have better control and view of the textual file, For e.g., layer 1 or layer 2, etc of a slab. How can I achieve this? Thank You.

[Anders Blom]

It's not possible to have the exact same order as in the coordinate list because VASP demands that the atoms are grouped by chemical elements, i.e. you must have all Ni atoms after each other, and then the Si atoms, and then H, and so on (the order of the elements can be changed though).

That said, if for instance all atoms are already of the same kind, one can argue that it should keep the order as in the coordinate list... or at least within each group of atoms (same element). We can look into that - right now it random, I agree.

[mmg016]

Dear Anders,

Thank you for your response.
Yes, that is exactly what I mean - atoms of the same kind to be written in the text file according to a particular order, like for e.g., each layer of a slab (of one particular type of atoms) is grouped together. This would be very helpful.

[Anders Blom]

I have filed a request that we improve this

[mmg016]

Thank you, Anders.