| While running Electron transfer calculations on various molecules, I accidently concatenated an input file with itself and got a different value for the Electron Transfer Coupling Energy. I am not sure why this would happen; it should simply rerun the calculation. I reran the calculation multiple times separately, and I get a coupling energy consistent with the single run. I tested this on the benzene dimer: 
 
 start testH          1.21943       -0.16516        2.15996geometry BENZI units angstroms NOCENTER NOAUTOZ NOAUTOSYM
 
 C          0.68248       -0.09239        1.20875
 C         -0.70744       -0.03519        1.19732
 H         -1.26436       -0.06297        2.13935
 C         -1.38982        0.05722       -0.01143
 H         -2.48356        0.10214       -0.02044
 C         -0.68242        0.09248       -1.20876
 H         -1.21940        0.16520       -2.15990
 C          0.70748        0.03523       -1.19730
 H          1.26413        0.06285       -2.13946
 C          1.38989       -0.05717        0.01143
 H          2.48360       -0.10222        0.02049
 end
 
 geometry BENZJ units angstroms NOCENTER NOAUTOZ NOAUTOSYMH          2.47117       -4.36748       -0.36219
 C          1.37747       -4.32248       -0.37129
 H          1.20697       -4.43048        1.77731
 C          0.67007       -4.35768        0.82611
 H          1.25167       -4.20248       -2.52219
 C          0.69507       -4.23008       -1.57999
 C         -0.71983       -4.30048        0.81461
 C         -0.69483       -4.17278       -1.59149
 H         -1.27683       -4.32828        1.75671
 C         -1.40223       -4.20808       -0.39409
 H         -1.23183       -4.10008       -2.54259
 H         -2.49603       -4.16318       -0.40309
 end
 
 geometry BENZIJ units angstroms NOCENTER NOAUTOZ NOAUTOSYMH          1.21943       -0.16516        2.15996
 C          0.68248       -0.09239        1.20875
 C         -0.70744       -0.03519        1.19732
 H         -1.26436       -0.06297        2.13935
 C         -1.38982        0.05722       -0.01143
 H         -2.48356        0.10214       -0.02044
 C         -0.68242        0.09248       -1.20876
 H         -1.21940        0.16520       -2.15990
 C          0.70748        0.03523       -1.19730
 H          1.26413        0.06285       -2.13946
 C          1.38989       -0.05717        0.01143
 H          2.48360       -0.10222        0.02049
 H          2.47117       -4.36748       -0.36219
 C          1.37747       -4.32248       -0.37129
 H          1.20697       -4.43048        1.77731
 C          0.67007       -4.35768        0.82611
 H          1.25167       -4.20248       -2.52219
 C          0.69507       -4.23008       -1.57999
 C         -0.71983       -4.30048        0.81461
 C         -0.69483       -4.17278       -1.59149
 H         -1.27683       -4.32828        1.75671
 C         -1.40223       -4.20808       -0.39409
 H         -1.23183       -4.10008       -2.54259
 H         -2.49603       -4.16318       -0.40309
 end
 
 BASIS * LIBRARY 6-31g
 end
 SET geometry  BENZI
 CHARGE  0
 SCF
 NOPEN 0
 UHF
 SINGLET
 VECTORS INPUT atom OUTPUT BENZI_0.movecs
 maxiter 100
 end
 TASK SCF
 
 
 SET geometry  BENZI CHARGE  1
 SCF
 NOPEN 1
 UHF
 DOUBLET
 VECTORS INPUT atom OUTPUT BENZI_1.movecs
 maxiter 100
 end
 TASK SCF
 
 
 SET geometry  BENZJ CHARGE  0
 SCF
 NOPEN 0
 UHF
 SINGLET
 VECTORS INPUT atom OUTPUT BENZJ_0.movecs
 maxiter 100
 end
 TASK SCF
 
 
 SET geometry  BENZJ CHARGE  1
 SCF
 NOPEN 1
 UHF
 DOUBLET
 VECTORS INPUT atom OUTPUT BENZJ_1.movecs
 maxiter 100
 end
 TASK SCF
 
 
 SET geometry  BENZIJ CHARGE  1
 SCF
 SYM OFF
 ADAPT OFF
 NOPEN 1
 UHF
 VECTORS INPUT FRAGMENT BENZI_0.movecs BENZJ_1.movecs OUTPUT BENZI_0BENZJ_1.movecs
 NOSCF
 end
 TASK SCF
 
 
 SET geometry  BENZIJ CHARGE  1
 SCF
 SYM OFF
 ADAPT OFF
 NOPEN 1
 UHF
 VECTORS INPUT FRAGMENT BENZI_1.movecs BENZJ_0.movecs OUTPUT BENZI_1BENZJ_0.movecs
 NOSCF
 maxiter 100
 end
 TASK SCF
 
 
 SET geometry  BENZIJ CHARGE  1
 ET
 VECTORS REACTANTS BENZI_0BENZJ_1.movecs
 VECTORS PRODUCTS BENZI_1BENZJ_0.movecs
 end
 TASK SCF ET
 
 
 SET geometry  BENZIJ CHARGE  1
 ET
 VECTORS REACTANTS BENZI_1BENZJ_0.movecs
 VECTORS PRODUCTS BENZI_0BENZJ_1.movecs
 end
 TASK SCF ET
 
 
 For each case of hole transfer from BENZI-> BENZJ and BENZJ-> BENZI I get:
 
 Electron Transfer Coupling Energy |V(RP)|      0.0026485746
 
 But when I concatenate the above input file with itself and run the calculation I get:
 
 Electron Transfer Coupling Energy |V(RP)|      0.0044280336
 |