Hi everyone, I calculated the electronic coupling for the same donor–acceptor system using standalone CDFT/direct coupling and CDFT-CI, but the resulting coupling values differ significantly. In both calculations, the Becke charge and spin populations satisfy the intended constraints. When I compared the Hamiltonian matrices, the main differences appeared in the diagonal terms, Hii and Hff. In the Q-Chem manual example for CDFT/direct coupling, the first two jobs generate the two constrained diabatic states, while the third job evaluates the coupling using the HF method. My concern is that, although the diabatic energies are obtained at the DFT level in the first two jobs matched what I got from CDFTCI, the HF calculation in the third job seems to produce different Hamiltonian elements. Could someone clarify the methodological difference between standalone CDFT/direct coupling and CDFT-CI? I am sharing input files for both the approaches.
CDFT:
$molecule
-1 2
C 2.68641000 -0.43326000 -3.93764000
C 3.38058000 0.91782000 -4.20888000
C 3.88034000 1.57322000 -2.90874000
C 2.72404000 1.74215000 -1.90951000
C 2.02042000 0.41030000 -1.64388000
C 1.52629000 -0.23478000 -2.94239000
H 3.42781000 -1.08212000 -3.43973000
H 2.67521000 1.59934000 -4.70460000
H 4.22598000 0.77975000 -4.89228000
H 4.60695000 0.88516000 -2.45426000
H 2.00089000 2.46157000 -2.31674000
H 3.10554000 2.16857000 -0.97495000
H 1.18068000 0.56197000 -0.95716000
H 2.71878000 -0.27357000 -1.14247000
H 1.04697000 -1.19576000 -2.72540000
H 0.75978000 0.41525000 -3.38853000
C 2.25567000 -1.10964000 -5.22643000
C 2.84670000 -2.29619000 -5.68842000
C 2.50041000 -2.90277000 -6.88317000
C 1.49838000 -2.35947000 -7.75749000
C 0.89327000 -1.15153000 -7.26645000
C 1.26325000 -0.57238000 -6.06821000
C 1.14280000 -2.96018000 -9.00827000
C 1.75445000 -4.17331000 -9.49510000
C 1.41855000 -4.73603000 -10.70929000
C 0.44908000 -4.16064000 -11.55417000
C -0.17225000 -2.97871000 -11.10424000
C 0.14944000 -2.40119000 -9.89321000
H 3.62104000 -2.75294000 -5.07277000
H 3.02019000 -3.81591000 -7.15817000
H 0.11586000 -0.66244000 -7.84643000
H 0.77260000 0.34635000 -5.75248000
H 2.51075000 -4.67285000 -8.89666000
H 1.92245000 -5.65094000 -11.01885000
H 0.19003000 -4.60890000 -12.50805000
H -0.92947000 -2.50081000 -11.72468000
H -0.37179000 -1.49141000 -9.60928000
C 3.96112000 3.93809000 -3.78835000
C 4.59658000 2.88220000 -3.17431000
C 5.95256000 3.04289000 -2.78334000
C 6.62711000 4.21570000 -3.00699000
C 5.98553000 5.31114000 -3.64104000
C 4.62669000 5.16572000 -4.03783000
C 3.97688000 6.25790000 -4.67557000
C 4.64518000 7.43306000 -4.90580000
C 5.99812000 7.57698000 -4.50946000
C 6.65142000 6.54104000 -3.89232000
H 2.92236000 3.84608000 -4.09783000
H 6.45850000 2.21250000 -2.29785000
H 7.66500000 4.31989000 -2.70211000
H 2.93941000 6.14358000 -4.97804000
H 4.14020000 8.26083000 -5.39386000
H 6.51489000 8.51308000 -4.69656000
H 7.68927000 6.64618000 -3.58755000
$end
$rem
METHOD = wB97M-V
BASIS = 6-311+G**
GUI = 2
SCF_MAX_CYCLES = 800
CDFT = true
CDFT_PRINT = TRUE
CDFT_BECKE_POP = TRUE
CDFT_THRESH = 8
BECKE_SHIFT = UNSHIFTED
THRESH = 14
S2THRESH = 14
SAVE_SUBSYSTEM = 10
POINT_GROUP_SYMMETRY = False
SOLVENT_METHOD = PCM
MEM_TOTAL = 248000
MEM_STATIC = 4000
$end
$cdft
1.0
1.0 17 37
1.0
1.0 17 37 s
$end
$pcm
THEORY CPCM
heavypoints 590
method swig
radii bondi
solver inversion
$end
$solvent
DIELECTRIC 7.5
OPTICALDIELECTRIC 1.97
$end
@@@
$molecule
read
$end
$rem
METHOD = wB97M-V
BASIS = 6-311+G**
GUI = 2
CDFT = true
CDFT_PRINT = TRUE
CDFT_BECKE_POP = TRUE
CDFT_THRESH = 8
BECKE_SHIFT = UNSHIFTED
THRESH = 14
S2THRESH = 14
SAVE_SUBSYSTEM = 20
POINT_GROUP_SYMMETRY = False
SOLVENT_METHOD = PCM
MEM_TOTAL = 248000
MEM_STATIC = 4000
$end
$cdft
1.0
1.0 38 54
1.0
1.0 38 54 s
$end
$pcm
THEORY CPCM
heavypoints 590
method swig
radii bondi
solver inversion
$end
$solvent
DIELECTRIC 7.5
OPTICALDIELECTRIC 1.97
$end
@@@
$molecule
read
$end
$rem
METHOD = HF
BASIS = 6-311+G**
POINT_GROUP_SYMMETRY = False
SCF_GUESS = read
SOLVENT_METHOD = PCM
STS_DC = true
$end
$pcm
THEORY CPCM
heavypoints 590
method swig
radii bondi
solver inversion
$end
$solvent
DIELECTRIC 7.5
OPTICALDIELECTRIC 1.97
$end
CDFTCI
$molecule
-1 2
C 2.68641000 -0.43326000 -3.93764000
C 3.38058000 0.91782000 -4.20888000
C 3.88034000 1.57322000 -2.90874000
C 2.72404000 1.74215000 -1.90951000
C 2.02042000 0.41030000 -1.64388000
C 1.52629000 -0.23478000 -2.94239000
H 3.42781000 -1.08212000 -3.43973000
H 2.67521000 1.59934000 -4.70460000
H 4.22598000 0.77975000 -4.89228000
H 4.60695000 0.88516000 -2.45426000
H 2.00089000 2.46157000 -2.31674000
H 3.10554000 2.16857000 -0.97495000
H 1.18068000 0.56197000 -0.95716000
H 2.71878000 -0.27357000 -1.14247000
H 1.04697000 -1.19576000 -2.72540000
H 0.75978000 0.41525000 -3.38853000
C 2.25567000 -1.10964000 -5.22643000
C 2.84670000 -2.29619000 -5.68842000
C 2.50041000 -2.90277000 -6.88317000
C 1.49838000 -2.35947000 -7.75749000
C 0.89327000 -1.15153000 -7.26645000
C 1.26325000 -0.57238000 -6.06821000
C 1.14280000 -2.96018000 -9.00827000
C 1.75445000 -4.17331000 -9.49510000
C 1.41855000 -4.73603000 -10.70929000
C 0.44908000 -4.16064000 -11.55417000
C -0.17225000 -2.97871000 -11.10424000
C 0.14944000 -2.40119000 -9.89321000
H 3.62104000 -2.75294000 -5.07277000
H 3.02019000 -3.81591000 -7.15817000
H 0.11586000 -0.66244000 -7.84643000
H 0.77260000 0.34635000 -5.75248000
H 2.51075000 -4.67285000 -8.89666000
H 1.92245000 -5.65094000 -11.01885000
H 0.19003000 -4.60890000 -12.50805000
H -0.92947000 -2.50081000 -11.72468000
H -0.37179000 -1.49141000 -9.60928000
C 3.96112000 3.93809000 -3.78835000
C 4.59658000 2.88220000 -3.17431000
C 5.95256000 3.04289000 -2.78334000
C 6.62711000 4.21570000 -3.00699000
C 5.98553000 5.31114000 -3.64104000
C 4.62669000 5.16572000 -4.03783000
C 3.97688000 6.25790000 -4.67557000
C 4.64518000 7.43306000 -4.90580000
C 5.99812000 7.57698000 -4.50946000
C 6.65142000 6.54104000 -3.89232000
H 2.92236000 3.84608000 -4.09783000
H 6.45850000 2.21250000 -2.29785000
H 7.66500000 4.31989000 -2.70211000
H 2.93941000 6.14358000 -4.97804000
H 4.14020000 8.26083000 -5.39386000
H 6.51489000 8.51308000 -4.69656000
H 7.68927000 6.64618000 -3.58755000
$end
$rem
METHOD = wB97M-V
BASIS = 6-311+G**
GUI = 2
SCF_MAX_CYCLES = 800
CDFTCI = TRUE
CDFTCI_PRINT = 2
CDFT_THRESH = 7
CDFTCI_SKIP_PROMOLECULES = TRUE
THRESH = 14
S2THRESH = 14
POINT_GROUP_SYMMETRY = FALSE
SOLVENT_METHOD = PCM
MEM_TOTAL = 248000
MEM_STATIC = 4000
$end
$cdft
1.0
1.0 17 37
1.0
1.0 17 37 s
-------------
1.0
1.0 38 54
1.0
1.0 38 54 s
$end
$pcm
THEORY CPCM
HEAVYPOINTS 590
METHOD SWIG
RADII BONDI
SOLVER INVERSION
$end
$solvent
DIELECTRIC 7.5
OPTICALDIELECTRIC 1.97
$end