[xcrysden] negative isovalue

[Silviu Zilberman]

Hello Tone,

Thank you for a great software and for putting up this mailing list!

I have a question related to the meaning of the "isovalue" used in 
density plots.  I have molecular orbitals, calculated at gamma-point 
using PWSCF. I generated xsf files for |psi|^2 that preserve the sign, 
and in particular one of the orbitals have a maximal value of 0.000065 
and minimal value of -0.270350, i.e. a negative sign of the orbital.

When I specify isovalue of -0.001, would it enclose the negative part of 
the density (rho<-0.001) or the positive part (rho>-0.001)? (I hope I 
made myself clear). I know I can just plot |psi|^2 without preserving 
the sign, but it's more convenient for batch processing to keep it.

Thanks, Silviu.