[Pw_forum] about example 03 (Al relaxation)

[Aritz Leonardo]

Hello:

I have a short question. I am trying to relax Magnesium surfaces in the 
same way as example03 for aluminium.

When I run the example what I don't understand is that only Z-direction 
is relaxed. How come that atoms do not relax moving in X and Y 
direction? As far as I understand from the input, there are not fixed 
directions of atom positions so in principle they should all move in 3 
directions.

regards