## Pseudo atoms

A 'P' line should look like:

    P Pseudo_atom_index Pseudo_atom_type Numb_real_atoms Real_atom_indices

These parameters encode the pseudo atom information as given in Section 5.3.2. `Pseudo_atom_index` is the atom index, which should be a number between NATM+1 and NATM+NPSEUDO, where NATM is the number of real atoms in the model, and NPSEUDO the number of pseudo atoms. `Pseudo_atom_type` is the numerical pseudo atom type, as given in Table B.3. The pseudo atom is defined as an average of `Numb_real_atoms`, of indices `Real_atom_indices`. For example,

    P    144   1   3    120 121 122

creates a pseudo atom at index 144, which is a gravity center of the 3 atoms 120, 121 and 122.

Table B.3: Numerical pseudo atom types
Numeric pseudo atom type | Pseudo atom type
1 | `pseudo_atom.gravity_center`
2 | `virtual_atom.ch1`
3 | `virtual_atom.ch1a`
4 | `pseudo_atom.ch2`
5 | `virtual_atom.ch2`
6 | `pseudo_atom.ch31`
7 | `pseudo_atom.ch32`