[QE-users] definition of the hyperfine coupling constant in QE-GIPAW

[Davide Ceresoli]

Dear Gregor,
     the hyperfine coupling should be multiplied by the number
of unpaired electrons (2*S_z). It also assumes I=1/2.

In the past I checked that GIPAW yields the same results of ORCA
and Gaussian for molecules in the case S = I = 1/2. I can re-check that.

Best.
Davide



On 12/18/20 10:22 AM, Gregor Mali wrote:
> Hello.
> 
> 
> Isotropic hyperfine coupling constants A_iso, calculated by QE-GIPAW, can differ 
> by a large factor from A_iso, obtained by Orca. The factor depends on the number 
> of unpaired electrons in the unit cell (used in QE) and in the cluster model 
> (used in Orca). In Orca, A_iso is proportional to spin-density at the position 
> of a nucleus divided by <S_z>. <S_z> is the maximum value of the z component. 
> What is the definition of A_iso in QE-GIPAW? Is it perhaps proportional 
> to spin-density multiplied by S(S+1)/<S_z>?
> 
> 
> Thanks in advance!
> 
> 
> Gregor Mali
> 
> National Institute of Chemistry
> 
> Ljubljana, Slovenia