[Pw_forum] what atoms are counted by ntype

[Michele Lazzeri]

novikov.dmitri at tiax.biz wrote:

> Could someone tell me please what atoms are counted as "different type":
> crystallographycally different or chemically(and spin direction) different?

Two atoms are of the same "type" if you are describing them with
the same pseudopotential.
Two atom of the same "type" can be crystallographycally equivalent
or not. At the end of the calculation they can result as being chemically
different.

You can decide to describe two crystallographically
equivalent atoms with two different pseudopotentials.
In this case the code will not recognize the two atoms as equivalent.

Let's make a stupid  example, if you want to compute
a molecule of CH3-CH3
you will use two different pseudopotentials: one  for C and one for H,
and you will have ntyp=2.
You can decide (for some weird reason) to use two different pseudopotentials
to describe the two C atoms.
In this case you will have ntyp=3.


Best regards,