[Pw_forum] more about phonon frequencies are different when treated as insulator or metal

[Nicola Marzari]

> Are you sure, that the cold smearing of Marzari-Vanderbilt is positive
> definite?

I'm positively sure.

			nicola

PS: sorry for the abrupt answer; I hope I didn't sound too negative.

More seriously, let us know more on the problems you encountered -
as Stefano mentioned, it is possible, at least in principle, that
in a molecule with discrete levels or in an insulator with very
sparse k-point sampling there could be two allowed values for the
fermi energy, due to the non-monotonicity of the occupation function.
This, in iteself, shouldn't create a problem, unless the code bounces
back and forth between the two Fermi energy between interations.
Still, it seems an extremely unlikey possibility.


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Prof Nicola Marzari   Department of Materials Science and Engineering
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