UT theoretical chemistry code forum

Dear Prof. Graeme,

I'm trying to find proper fft grid resolution for my system - Hg and hematite slab including core charge. Original grid size was 72x72x800 in CHGCAR.
I increased grid size to 108x108x800, 216x216x800, 288x288x800, 432x432x800 and 800x800x800 with LAECHG=.TRUE and then followed the description below.

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By adding the LAECHG=.TRUE. to the INCAR file, the core charge is written to AECCAR0 and the valance charge to AECCAR2. These two charge density files can be summed using the chgsum.pl script:

chgsum.pl AECCAR0 AECCAR2
The total charge will be written to CHGCAR_sum.
The bader analysis can then be done on this total charge density file:

bader CHGCAR -ref CHGCAR_sum
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When I checked ACF.dat for all cases, there were electron loss in high NGX(Y,Z)F.
For example, in 72x72x800, 108x108x800, and 216x216x800 grid sizes,
I've got 'NUMBER OF ELECTRONS: 308.00000'.
But in 288x288x800, 432x432x800, and 800x800x800 cases,
I've got 'NUMBER OF ELECTRONS: 288.00000'.

How come this electron loss happens, especially in finer grid sizes? In all cases, I used same original data and only did single point calculation with new grid setting.
Thank you for the help in advance!

Best,
Ji-Eun

This doesn't make any sense to me, unless you have tried using different pseudopotentials in your different calculations. The fact that both electron sums (288 and 308) are integers supports this idea. So check if some _pv or _sv were used in the calculation which sums to 308.