[Pw_forum] (no subject)

[Julen Ibanez Azpiroz]

Hello

I am trying to relax a system with unit cell made of 24 silicon atoms and 2
talium atoms, one in each edge. I wish the system to be a surface, so the
unit cell has vacuum between the talium atoms so that they do not "see" each
other. I tried to relax it following the Example03 of Quantum Espresso which
is a surface of  "al001". In the example there are two methods, I followed
the first one, the one of the "bfgs" method. When I use Scalar_Relativistic
pseudopotentials (for both atoms) it is Ok, after some trials the system
relaxes. However, when I use Relativistic pseudopotentials (for both atoms)
the system cannot relax, after many trials the system repeats the atomic
configuration and stops. I have tried both, to let all the atoms move and to
let move just a few of the surface, keeping the other fixed, but it does not
work anyway. The most I can get is that the force in every atom is smaller
than 0.01Ry/au. Both pseudopotentials work allright in simpler models. I
would appreciate any suggestion. Thank you very much

Julen

UPV/EHU, Fisica de la Matertia Condensada
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