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

[W. YU]

Dear Paolo and all,

In order to see whether the value of degause was too
large in my previous post with the same title, I have
caculated the phonon frequencies of Si at gamma and X
points using different values of degause from
0.05-0.005, even a value of 0.005 will affect the
frequencies to some extend. This value sure will fall
in the band gap of Si and in theory will have no
effect even if I treat Si as a metal instead of an
insulator. But the results are dispointing.

If I increase the number of K points, the results will
improve. Must I use a much larger number of K points
when I am treating an insulator as a metal instead of
an insulator in order get similar results? Why so?



		
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