[CP2K-user] Hirshfeld charges, neutral system with no zero total Hirshfeld charge

[Lucas Lodeiro]

Hi all,
I want to obtain Hirshfeld charges for a neutral bulk liquid system (372
atoms), but when I compute the Hirshfeld charges, the total system charge
is different to zero.
To obtain the charges I set:
                &PRINT
                        &HIRSHFELD
                                FILENAME
                                SELF_CONSISTENT .TRUE.
                                SHAPE_FUNCTION  DENSITY
                        &END HIRSHFELD
                &END PRINT
I explore the four combinations between nonSCf / SCF and density / gaussian
shape functions. The SCF does not change the behavior of total charges
(just correct the atomic charges as the reference paper explains). The
density shape function corrects the total charge from -1.1 to -0.167, but
it still remains different from zero. I compute the total charge of an
isolated molecule (the charge is different of zero too, but little) and
multiply this value for the number of molecules in the bulk liquid system,
and I get -0.084, this is a half the bulk total charge.
I understand there is numerical "noise" and approximations (just 3
decimals), but I am not pretty sure if this is "normal" or I am missing
something.

I think if I use more accurate SCF convergence for Hirshfeld charges it
could be corrected, but I do not find any parameter that chose it.

Is what I am getting correct?

Regards - Lucas Lodeiro
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