[gpaw-users] RPA: RuntimeWarning: invalid value encountered in sqrt

[Thomas Stenbæk Jauho]

Hi,

I am doing RPA calculations for Na and 30 other systems. I have attached 
the scripts for Na, the RPA calculation is separated in three separate 
files; a PBE calculation, a diagonalization and the RPA.

While 30 systems do work, Na does not. I receive the following error:

/home/niflheim/s093006/gpaw/gpaw/response/chi0.py:302: RuntimeWarning: 
invalid value encountered in sqrt
x_m = (-2 * df_m * deps_m / (omega.imag**2 + deps_m**2))**0.5

I gather that it means that the square root (omega.imag**2 + 
deps_m**2))**0.5 receives a negative argument, but I don't know why.

Previously I experienced the same problem with Li, but I resolved the 
issue by setting occupations=FermicDirac(0.01) i GPW(...) when making 
the DFT calculation. But this does not help for the Na system.

Any help will be highly appreciated!

/Thomas
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