[Pw_forum] Charge difference query

[Kenneth Wong]

Dear PWscf,

I wish to get some help regarding the calculation of the charge difference.
For example, if H2O was adsorbed onto TiO2 i want to see the charge
difference this is how i would go about it

Charge density of
a. (H2O + TiO2)
b. (TiO2)
c. (H2O)
Charge density difference =  a - (b+c)

So i would save the the a, b, c, intermediate files all in e.g.
separate calculation

&inputPP
filplot='inter(1)'
                          ...........then 'inter(2) then 'inter(3)'
(i guess they will all have to be in different names? inter(1), inter(2),
inter(3) as a, b, c, respectively)

Now, here is where i am lost.....
&plot
nfile = 3
filepp(3)=inter,
weight(3) =weight(1)*rho(1)  -  ( weight(2)*rho(2)+weight(3)*rho(3)),

i don't know what to do in this section, in regards to how to use weight(i),
filepp(i)


Thank you very much,

regards, Ken.
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