Boundary conditions -reg

[GJK]

Hi,

In ATK 12.8 we are having three options in the Poisson Solver
1.Multigrid
2.FF2D
3.FFT

What solver should be selected for
1.Molecular Optimization
2.Device Optimization
3.Bulk optimization

Thanks in Advance

[Umberto Martinez]

device: use FFT2D unless you have spatial regions, then Multigrid.
bulk: FFT unless it is charged. In that case you will need Multigrid
molecule: Multigrid, multipole

then there are some special cases that you may consider, see for example the slab calculations in this tutorial: Tuning the work function of silver by deposition of ultrathin oxide layers

[GJK]

Kindly explain me about spatial regions in a device and about multipole

[GJK]

Hi,

Kindly provide me an explanation of your following reply-
device: use FFT2D unless you have spatial regions,
bulk: FFT unless it is charged
molecule: Multigrid, multipole

Give some references or suggestions

Thanks in advance