NMR calculations with NWChem quantum chemistry program I tried experimenting with some ab initio NMR calculations using the NWChem program. I used quinuclidine as a simple test case. The input file was:

echo
start quinuclidine_b3ylp_opt_nmr_shift

geometry
  c         -6.06576        0.97412       -0.15301
  c         -5.70979        1.98552       -1.28158
  c         -4.36490        2.65888       -0.91745
  h         -6.47615        2.78876       -1.35616
  h         -5.68491        1.45114       -2.25601
  c         -3.37563        1.54341       -0.50314
  c         -3.86410        0.94013        0.84625
  h         -2.33065        1.90335       -0.38494
  h         -3.37977        0.77674       -1.30967
  n         -5.29417        1.27496        1.08291
  h         -3.26800        1.37762        1.67961
  h         -3.67643       -0.15484        0.87417
  h         -5.79345       -0.05430       -0.48418
  h         -7.16227        0.96043        0.02635
  c         -5.40220        2.73070        1.37047
  c         -4.60680        3.55788        0.31857
  h         -5.06760        2.98401        2.39936
  h         -6.47931        3.01065        1.31755
  h         -3.96835        3.24945       -1.77113
  h         -3.61077        3.85719        0.71410
  h         -5.16983        4.48719        0.08363
end

basis
 * library 6-311G
end

dft
 xc b3lyp
end

title "Quinuclidine B3LYP/6-311G geom opt nmr shift"
task dft optimize

basis
 * library 6-311G
end
dft
 xc b3lyp
end

property
 gshift
 shielding
end

task dft property


Next, I calculated the chemical shift of the TMS standard:

echo
start tms_b3lyp_opt_freq_nmr_shift

geometry units angstroms
  si  -5.37335102864362      2.43869139121700     -0.00017138545369
  c   -3.50689688966580      2.43868715601638     -0.00001133876668
  c   -5.99529466705065      4.19430001974021      0.12209335653192
  h   -5.64408778702798      4.67985919142380      1.04819971762123
  h   -7.09781476514675      4.22936546250064      0.12467467866764
  h   -5.64435465416627      4.80382888763710     -0.72767673129762
  h   -3.10677010278341      2.89237170000804      0.92240456642084
  h   -3.10633327621776      3.01074016686707     -0.85387463583008
  h   -3.10622471891726      1.41321522592654     -0.06819713587793
  c   -5.99568159818493      1.45555000740651      1.45925444723856
  c   -5.99571944212990      1.66683194553091     -1.58150765777166
  h   -5.64537419258706      1.88774171172852      2.41177722402156
  h   -5.64408400205021      0.41082962309567      1.41778721376507
  h   -7.09821437068132      1.43547142531899      1.48770835119311
  h   -5.64584598058862      2.22683552653798     -2.46512226305553
  h   -7.09824537965055      1.65038972286304     -1.61218398701376
  h   -5.64368714450789      0.62658083618162     -1.68513442039297
end

basis
 * library 6-311G
end

dft
 xc b3lyp
end

title "TMS VWN5/aug-cc-pVDZ geom opt nmr shift"
task dft optimize

basis
 * library 6-311G
end
dft
 xc b3lyp
end

property
 gshift
 shielding
end

task dft property


However, the resulting chemical shifts are terribly off from the experimental ones. Am I doing an obvious mistake or is the big deviation just the best you can get out of such calculations? What is your experience and approach to ab initio NMR calculations (i.e. chemical shifts and coupling constants)?
Those calculations are tricky because some functionals work well, others don't, some basis sets work well while even a better basis might give bad results and so on.

We did some studies in the past using the GIAO Method in G09 with B3LYP and 6-311+G(2d,p) als basis for the NMR calculations and M06-2X/6-311++G(d,p)for geometry optimization. And that worked quite well. However, we always used solvated systems (PCM) which seems to be the common way to do it. Try to reoptimize in solvent and run the NMR calculation in solvent if that's possible in NWChem.