Dear Michal
open-shell metal complexes usually show instabilities in scf cycles.
This may be generally due to jumps between almost equivalent or
degenerate electronic states, but also to the strongly correlated
nature of d electrons weakly coupled with the ligand electronic states
(a typical Mott-Hubbard problem...!), with the delocalization error
leading to a wrong "metallic" description of the partially occupied d
band. In the former case, there is no harm in using
occupations='smearing' with a Gaussian smearing to facilitate
convergence, as long as the smearing is small enough to avoid the
spread of electrons across the HOMO-LUMO gap. You can even use
tot_magnetization to force the convergence to any sensible magnetic
configuration of the system. In the latter case, you should be almost
always able to reach the converge using a Gaussian smearing, but you
should closely check the results and maybe use some local (e.g. DFT+U)
or global (e.g. EXX functionals like B3LYP, PBE0, ...) correction to
improve the description of the system.
HTH
Giuseppe
Quoting Michal Husak <michal.hu...@vscht.cz>:
Hi alll
I was up to now working with fully organic system - so I handled
then with fixed occupany ...
I was working with:
OCCUAPTIONS: fixed
I need to work now with organometalic systems - they contain group
like e.g. Fe O6 (iron coordinated by 6 oxygen + organic parts) ...
I belive it is still an insulator, but the fixed occupancy lead to
non-converging SCF (oscillating between 2 states) ...
Can anybody tell me what everything do i need to change in the setup
to handle organometalic compounds ?
Is simple following modification everything I need to do ?:
OCCUAPTIONS: smearing
Michal Husak
UCT Prague ... _______________________________________________
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GIUSEPPE MATTIOLI
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people and expresses its concerns about the devastating
effects that the Russian military offensive has on their
country and on the free and peaceful scientific, cultural,
and economic cooperation amongst peoples
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Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
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