[DFTB-Plus-User] About co-ordinates and lattice vectors

[Tej Raj Karki]

Dear all,
I am a novice in the DFTB+. I want to apologize for the questions but I
want to learn it most importantly. I went through a tutorial on the DFTB+
and saw different examples. But I was very concerned about how the
coordinates and lattice vectors were chosen for the given examples. For
example, the coordinates used in the first calculation with DFTB+
https://dftbplus-recipes.readthedocs.io/en/latest/basics/firstcalc.html
Similarly, there are other coordinates and lattice vector input in TiO2
https://dftbplus-recipes.readthedocs.io/en/latest/basics/bandstruct.html
Thus, my first question is how can we know or determine the coordinates and
lattice vectors of a molecule. Similarly, my second confusion is how to
know the number of atoms in a molecule? For instance, we took 3 atoms in
water and 6 in TiO2. It is due to the structure of the molecule?

Hope you understand my queries.
Sorry for the inconvenience.

Thank you

Sincerely
Tej Raj Karki
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