[CPMD-list] Energy and lattice constant

[Oleksandr Shepelyev]

Dear CPMD Users!

I have successfully implemented the PW91 (GGA) density functional into
CPMD code. Results for single Fe atom are close to normconserving
Goedecker PP. Also I found the evident energy minimum at interatomic
distance close to experimental lattice constant. But calculations for
54 and 128 atoms show that decreasing of the lattice constant leads to
decreasing of energy and the minimum of energy is not evident. For 54
atoms after passing the point which is close to lattice constant some
increasing of energy was found, but at the next point the energy starts
to fall down.
Does this mean that my lattice is unstable? Or as I found in literature
I must study my lattice using the experimental lattice constant?

Also the Total Integrated Spin Density looks too high (33 for 54 atoms,
7.6 for 128 atoms but 0. for 1 atom) in my results.

Sincerely yours,
Alex Shepelyev