[Pw_forum] total potential plot

[Matteo Cococcioni]

Dear all,

I have two technical questions. I'm interested in a (2d or 3d) plot of 
the total potential the electrons are subjected to
(V_ext + V_H + V_xc).

1) If I read Doc/INPUT_PP I find:

   Variable:       plot_num
 
   Type:           INTEGER
   Description:    selects what to save in filplot:

                      0  = charge

                      1  = total potential V_bare+V_H + V_xc

                      2  = local ionic potential

                      3  = local density of states at e_fermi

                      4  = local density of electronic entropy

                      5  = STM images

                      6  = spin polarization (rho(up)-rho(down))

                      7  = |psi|^2


So, I guess, the total potential is the sum of two files obtained with a 
pp.x run with plot_num = 1 and a second with plot_num = 2.
If I do this the result is reasonable (e.g., the potential is attractive 
around the ions and positive in other regions where
electronic charge mostly concentrates). However I'm not 100% sure this 
is right. For example, is there any overlap (redundance) between
the quantities obtained with plot_num = 1 and plot_num = 2? I have given 
a look to the routines but doesn't look too easy to understand....

2) is there any known reason why plotrho fails when trying to make a 2D 
plot of the potential? following example05 I can obtain
2D plots of the charge density with no problem, but not the potential. 
The files have the same format except for the fact that the potential
can go negative. is this the problem?

Thanks,

Matteo