For details, see the following reference:
"The electronic complexity of the ground-state of the FeMo cofactor of nitrogenase as relevant to quantum simulations" Zhendong Li, Junhao Li, Nikesh S. Dattani, C. J. Umrigar, and Garnet Kin-Lic Chan, J. Chem. Phys. 150, 024302 (2019). doi: https://aip.scitation.org/doi/10.1063/1.5063376 arXiv: https://arxiv.org/abs/1809.10307
Some explanations about how the FCIDUMP file is generated:
The DFT calculations and integral transformation were performed with the PYSCF package.
Geometry:
Fe 10.018000 -7.568000 56.109001
Fe 12.528000 -8.326000 55.692001
Fe 11.277000 -6.902000 53.853001
Fe 11.990000 -5.771000 56.166000
Fe 14.820000 -7.601000 54.671001
Fe 13.550000 -6.198000 52.848999
Fe 14.226000 -5.072000 55.094002
Mo 16.132000 -5.638000 53.306000
C 13.044000 -6.665000 54.723999
S 11.719000 -7.459000 57.646000
S 16.169001 -6.043000 55.618000
S 10.001000 -5.522000 55.134998
S 13.162000 -3.960000 56.627998
S 14.407000 -9.544000 55.750999
S 14.337000 -4.109000 53.098000
S 10.718000 -8.998000 54.466999
S 15.203000 -7.626000 52.453999
S 11.674000 -6.465000 51.712002
S 8.197000 -8.169000 57.320999
C 13.298000 -2.024000 50.055000
N 12.366000 -2.944000 50.620998
C 11.087000 -2.665000 50.879002
N 10.465000 -1.648000 50.319000
N 10.437000 -3.395000 51.761002
C 15.000000 -1.023000 59.625000
C 16.169001 -0.765000 58.679001
C 17.408001 -1.557000 59.002998
O 17.870001 -1.613000 60.158001
N 18.021999 -2.150000 57.976002
C 8.265000 -1.347000 60.679001
C 9.399000 -1.996000 59.963001
N 9.933000 -3.152000 60.439999
C 10.065000 -1.670000 58.792999
C 10.903000 -3.530000 59.608002
N 10.987000 -2.647000 58.599998
C 8.211000 -4.616000 49.907001
C 7.638000 -4.371000 51.291000
C 6.881000 -3.235000 51.567001
C 7.762000 -5.325000 52.312000
C 6.315000 -3.036000 52.811001
C 7.180000 -5.134000 53.570000
C 6.480000 -3.971000 53.827999
O 5.954000 -3.723000 55.074001
N 5.234000 -10.420000 55.743999
C 6.175000 -9.825000 56.689999
C 5.492000 -9.417000 57.998001
O 4.993000 -8.311000 58.167999
C 6.936000 -8.649000 56.117001
N 5.537000 -10.342000 58.952000
C 18.375999 -9.779000 57.895000
O 18.938999 -9.535000 58.952999
N 17.193001 -9.276000 57.611000
C 16.604000 -8.174000 58.390999
C 15.700000 -8.561000 59.548000
O 16.066999 -8.490000 60.719002
N 14.482000 -8.960000 59.175999
C 13.413000 -9.170000 60.129002
C 12.448000 -10.321000 59.819000
O 11.585000 -10.619000 60.638000
N 12.608000 -10.986000 58.669998
C 11.669000 -12.033000 58.242001
C 12.397000 -13.165000 57.548000
O 12.311000 -14.342000 57.938000
N 13.074000 -12.829000 56.459999
C 13.702000 -13.811000 55.596001
C 14.324000 -13.116000 54.386002
C 13.275000 -12.471000 53.491001
C 13.911000 -11.621000 52.422001
N 12.878000 -11.123000 51.516998
C 13.118000 -10.372000 50.460999
N 14.374000 -10.095000 50.109001
N 12.094000 -9.945000 49.705002
O 22.684000 -7.070000 47.084999
C 18.180000 -7.369000 50.759998
C 18.711000 -7.463000 52.162998
N 18.159000 -6.788000 53.228001
C 19.879999 -8.011000 52.627998
C 18.976999 -6.904000 54.275002
N 20.003000 -7.668000 53.919998
C 17.480000 -1.176000 54.216000
C 17.136999 -1.687000 52.838001
C 17.757999 -3.064000 52.515999
C 19.298000 -2.979000 52.311001
C 19.787001 -4.275000 51.637001
C 21.243001 -4.658999 51.755000
C 17.111000 -3.651000 51.271999
O 17.582001 -2.027000 55.126999
O 17.659000 0.041000 54.360001
O 21.753999 -5.267001 50.771999
O 21.844000 -4.408001 52.838001
O 16.628000 -4.810000 51.337002
O 17.166000 -2.989000 50.195999
O 17.490000 -3.979000 53.599998
O 15.888000 -4.907000 46.811001
O 19.811001 -2.775000 44.562000
O 21.295000 -1.675000 56.474998
O 14.797000 -5.542000 49.339001
O 20.999001 -7.558000 49.209999
O 21.018000 -4.234000 48.202000
O 18.273001 -3.799000 47.834000
O 24.264000 -5.111000 53.854000
O 18.688999 -0.721000 49.472000
O 20.888000 -4.190000 55.507000
O 19.867001 0.773000 55.806000
O 19.983999 2.139000 49.183998
O 19.601999 0.653000 51.790001
H 14.253909 -2.551439 49.902245
H 13.485333 -1.148637 50.707842
H 12.976245 -1.666277 49.058362
H 12.756517 -3.749057 51.133080
H 10.948382 -1.006864 49.696509
H 9.418611 -3.350350 51.840380
H 10.851817 -4.301103 52.064489
H 14.176828 -0.309351 59.447134
H 15.333467 -0.925316 60.673517
H 14.594556 -2.042045 59.487892
H 15.865440 -0.939269 57.629728
H 16.465566 0.302217 58.741955
H 17.747578 -2.051739 56.983900
H 18.886142 -2.654352 58.166876
H 7.943033 -0.415330 60.180924
H 8.542154 -1.100693 61.721569
H 7.393391 -2.026762 60.730390
H 11.631869 -2.750219 57.800192
H 9.950464 -0.842408 58.089483
H 11.523221 -4.427460 59.671513
H 8.474673 -3.670967 49.398976
H 7.479231 -5.140569 49.262567
H 9.119194 -5.242955 49.957698
H 6.731721 -2.478799 50.782532
H 8.369443 -6.224645 52.146371
H 5.741910 -2.119104 53.011911
H 7.324840 -5.870775 54.367803
H 5.546271 -2.840425 55.063551
H 5.750165 -10.676231 54.895864
H 4.564723 -9.698382 55.448024
H 6.922962 -10.606213 56.936088
H 6.237039 -7.808570 55.941648
H 7.401622 -8.936745 55.157491
H 6.037121 -11.218482 58.832310
H 5.164447 -10.123761 59.874931
H 18.781655 -10.466135 57.105626
H 16.704789 -9.500843 56.734897
H 16.043744 -7.544498 57.677036
H 17.429698 -7.586986 58.824307
H 14.219156 -8.808225 58.189655
H 12.783401 -8.263772 60.234252
H 13.872680 -9.367031 61.112602
H 13.256381 -10.608473 57.970429
H 11.174293 -12.420930 59.144023
H 10.895271 -11.603903 57.570696
H 13.174849 -11.839973 56.192474
H 14.473224 -14.370958 56.160710
H 12.945500 -14.559086 55.282907
H 15.032972 -12.341634 54.741837
H 14.913117 -13.854269 53.810118
H 12.641772 -13.254547 53.028674
H 12.605520 -11.821374 54.090680
H 14.436696 -10.768534 52.906517
H 14.648390 -12.199351 51.832233
H 11.938028 -11.063509 51.914966
H 14.531875 -9.489172 49.305241
H 15.069805 -9.986501 50.852478
H 12.200422 -9.064588 49.201927
H 23.601459 -6.857982 47.330021
H 22.249074 -6.194096 47.039440
H 18.955188 -7.698977 50.048433
H 17.905390 -6.332504 50.518737
H 17.264032 -7.973340 50.626379
H 20.628332 -8.602807 52.103837
H 18.853442 -6.425326 55.245736
H 16.033435 -1.787606 52.792646
H 17.426546 -0.972948 52.052632
H 19.528063 -2.102232 51.681236
H 19.759202 -2.868484 53.309073
H 19.247123 -5.115528 52.106350
H 19.502098 -4.271284 50.571493
H 16.780810 -4.624223 47.121885
H 15.433213 -5.151276 47.644086
H 19.980766 -3.723341 44.435067
H 19.321145 -2.766364 45.406260
H 21.109337 -1.750623 57.425786
H 20.759935 -0.882264 56.201074
H 15.501236 -5.269415 49.977894
H 14.144043 -5.981686 49.917945
H 21.703906 -7.489930 48.526249
H 21.149790 -6.782293 49.795777
H 21.232006 -4.616723 49.099190
H 21.241122 -3.291069 48.291377 \
H 19.195384 -4.089918 48.024181
H 17.876980 -3.527801 48.695535
H 24.697333 -5.483950 53.066151
H 23.382051 -4.837434 53.479899
H 18.953931 -0.321612 50.327834
H 18.115647 -1.481067 49.723219
H 20.992458 -3.241281 55.753084
H 21.160164 -4.239411 54.564410
H 20.330760 1.130055 55.030296
H 18.979135 0.500481 55.434638
H 19.940635 1.936802 50.139503
H 19.518351 1.363575 48.815374
H 20.354371 0.130718 52.119534
H 18.942524 0.622904 52.521728
H 20.831763 -7.852887 54.530690
H 9.545331 -1.367341 50.646139
H 11.144726 -10.137694 50.018567
C 23.292999 -8.105000 51.974998
C 24.523001 -7.559000 51.272999
O 25.587000 -8.169000 51.252998
N 24.365000 -6.351000 50.728001
C 25.365000 -5.756000 49.866001
C 24.761000 -4.521000 49.146000
O 22.260000 -7.893000 55.609001
H 17.491148 -3.347688 54.445403
H 22.481544 -8.230248 51.233996
H 22.943402 -7.372156 52.723626
H 23.534473 -9.061675 52.460204
H 23.421240 -5.901816 50.778903
H 26.261472 -5.456441 50.446366
H 25.720615 -6.508632 49.132117
H 24.470248 -3.748936 49.879990
H 23.848896 -4.798400 48.587383
H 25.488867 -4.081178 48.443117
H 21.937137 -7.439342 56.409331
H 22.855842 -7.224751 55.210211
Basis:
{'Fe':'TZP-DKH','Mo':'TZP-DKH','S':'TZP-DKH',
'C':'def2-SVP','H':'def2-SVP','O':'def2-SVP','N':'def2-SVP'}
Charge = -3, Spin = 35 (PYSCF convention: 2*S) for UKS/B3LYP with sf-X2C Hamiltonian and COSMO eps=4.0
Molecular orbitals: Split-Localized MOs, see MOs_plots (ordered by Genetic Algorithm implemented in the BLOCK code)
Active space information: CAS(113e,76o)