ABINIT Discussion Forums

Helle,
I am new to abinit.
I am doing ion relaxation for a slab containing 48 Si, 35 C, 26 O and 9 H atoms.
I need to fix some of them (like 20 of Si and 18 of C and 9H).
I don't know how I should use the 'natfix' variable. It means that I don't know how to specify the fixed atoms in the code.
I would appreciate if you could help.
M Alaaii

Hello,

natfix is the number of atoms that you want to fix. Then you have to tell abinit which atoms are fixed with the input array iatfix.

For example, if you have the water molecule and you want to fix the oxygen atom, you could do this :

natom 3
ntypat 2
znucl 1 8
typat 1 1 2
natfix 1
iatfix 3

if you want to fix the two hydrogen atoms, you just set
natfix 2
iatfix 1 2

Hope it helps

David