Re: Difference Charge Density ( No.1 ) 
 Date: 2010/12/10 15:30
 Name: T.Ozaki
 Hi,
> why not just fourier transform n(r) directly and mix n(q) before backtransforming > to get n(r) again..?
At least there are two evident reasons to do that.
(i) Since the Hartree potential by the difference charge density is much shallower than that by the original charge density, the numerical integration for constructing the Hamiltonian matrix elements can be performed by a coarser regular mesh.
(ii) The rearrangement of coulombic energy terms by Eq. 19 allows us to avoid the Ewaldtype sum for the sum of core repulsion energy, and to make the most of majority energy contributions short range.
> In the Charge Mixing Methods: Ver.1.0, under Section 3, "Kerker mixing in > momentum space", the kerker factor is defined as > w(q) = q^2 / (q^2 + q0^2) > where q0 = gamma*qmin
gamma is an adjustable parameter which controls the degree of suppression for charge sloshing, smaller less suppression, larger more suppression. In OpenMX gamma does correspond to scf.Kerker.factor.
Regards,
TO

