Methodology for calculating J-couplings


Click here for full thread
Clicked A Few Times
Hi, I just wanted to confirm whether the implementation of indirect spin-spin couplings (J-couplings) is based on CPDFT in nwchem. If so, the methodology should be the same as in Gaussian and I should get identical results. However, when I calculate the J-coupling constant for H2, the FC contribution comes out slightly different in Gaussian compared to nwchem. I'm using the following input:

start h2_nmr
geometry units angstroms
 H       3.18205 0.0 0.0
H 3.78205 0.0 0.0
end
basis
 H library cc-pvdz
end
dft
 xc pw91lda
grid lebedev
tolerances tight
odft
end
property
 spinspin 1 1 2
end
task dft property

Even though the implementations differ a little (nwchem has advanced support for relativistic calculations), I should still get the same results for light elements. Could I be missing something essential in the input?