I performed CDFT geometry optimization and frequency calculations using the wB97X-D/6-31G** level of theory, and the calculations converged successfully without any imaginary frequencies. However, when I switched to wB97X-D/aug-cc-pVDZ and started from the previously optimized geometry, the calculation struggled to converge, particularly in the CDFT iterations, even though I used the same charge constraints as before. I was wondering what could be causing this convergence issue with the larger basis set.
$molecule
-1 2
C -1.42918000 -0.96239000 0.76804000
C -2.38999000 -0.71226000 1.76600000
C -3.70560000 -1.14913000 1.62427000
C -4.13143000 -1.85459000 0.47942000
C -3.17186000 -2.05506000 -0.54573000
C -1.84751000 -1.61710000 -0.39853000
C -5.53834000 -2.41110000 0.37868000
C -6.40499000 -2.42655000 1.50529000
C -7.68584000 -2.97900000 1.42789000
C -8.14370000 -3.52641000 0.23498000
C -7.32045000 -3.52269000 -0.88879000
C -6.03398000 -2.97553000 -0.82153000
H -2.13738000 -0.20363000 2.68385000
H -4.36374000 -0.93104000 2.44836000
H -3.40477000 -2.58650000 -1.45246000
H -1.13542000 -1.83127000 -1.18664000
H -6.11684000 -2.04115000 2.46722000
H -8.32276000 -2.98808000 2.30432000
H -9.13551000 -3.95709000 0.18212000
H -7.67909000 -3.95077000 -1.81548000
H -5.45029000 -3.00755000 -1.72665000
C 1.95962000 1.08866000 0.40783000
C 2.73669000 0.08622000 1.27473000
C 1.95006000 -0.21545000 2.56750000
C 0.41894000 -0.16419000 2.37837000
C 0.04958000 -0.62625000 0.96187000
C 0.63046000 0.39117000 -0.08663000
H 1.67782000 1.93542000 1.07410000
H 3.75275000 0.41047000 1.57880000
H 2.86275000 -0.83570000 0.66318000
H 2.28153000 -1.22044000 2.90823000
H 2.19384000 0.51358000 3.37034000
H 0.04345000 0.87780000 2.49219000
H -0.02615000 -0.78895000 3.18227000
H 0.58406000 -1.59745000 0.84816000
H 0.78550000 -0.20734000 -1.00771000
H -0.09173000 1.20507000 -0.31605000
C 7.16138000 3.97122000 -1.47806000
C 6.97234000 3.86451000 -2.79543000
C 5.72940000 3.23890000 -3.30226000
C 4.79891000 2.76549000 -2.47038000
C 5.01576000 2.88113000 -1.01928000
C 6.12582000 3.46041000 -0.55808000
C 3.68281000 2.18694000 -2.91535000
C 2.68230000 1.60368000 -1.98745000
C 2.88208000 1.68365000 -0.65803000
C 4.10272000 2.39727000 -0.18276000
H 8.06545000 4.42568000 -1.08431000
H 7.72337000 4.23243000 -3.48720000
H 5.60345000 3.16492000 -4.37954000
H 6.30668000 3.55641000 0.51078000
H 3.49643000 2.09661000 -3.98304000
H 1.81844000 1.11273000 -2.41511000
H 4.24931000 2.50295000 0.89024000
$end
$rem
JOB_TYPE Optimization
METHOD wB97X-D
BASIS 6-31G(d,p)
SCF_CONVERGENCE 8
SCF_MAX_CYCLES 500
GEOM_OPT_MAX_CYCLES 200
SYMMETRY FALSE
SYM_IGNORE TRUE
GUI 2
CDFT TRUE
CDFT_PRINT TRUE
CDFT_BECKE_POP TRUE
CDFT_THRESH 8
BECKE_SHIFT UNSHIFTED
XC_GRID 2
$end
$cdft
1.0
1 1 21
$end
@@@
$molecule
read
$end
$rem
JOB_TYPE Freq
METHOD wB97X-D
BASIS 6-31G(d,p)
SCF_CONVERGENCE 8
SYMMETRY FALSE
SYM_IGNORE TRUE
SCF_GUESS READ
CDFT TRUE
CDFT_PRINT TRUE
CDFT_BECKE_POP TRUE
CDFT_THRESH 8
BECKE_SHIFT UNSHIFTED
XC_GRID 2
MEM_TOTAL 248000
MEM_STATIC 4000
$end
$cdft
1.0
1 1 21
$end
wB97X-D/aug-cc-pVDZ theory: I tried with just charge constraint and also adding spin constraints. But in both cases, it did not converge.
$molecule
-1 2
C -1.05752000 -1.39603000 0.86890000
C -1.98340000 -1.07935000 1.87509000
C -3.34662000 -1.24635000 1.73247000
C -3.93541000 -1.76228000 0.52891000
C -2.97880000 -2.08119000 -0.49354000
C -1.62407000 -1.89930000 -0.31619000
C -5.34379000 -1.95340000 0.36716000
C -6.31069000 -1.47018000 1.31826000
C -7.66613000 -1.66360000 1.15836000
C -8.19340000 -2.35200000 0.05048000
C -7.27318000 -2.83557000 -0.89836000
C -5.91515000 -2.64747000 -0.75702000
H -1.58975000 -0.70472000 2.81804000
H -3.98378000 -1.00946000 2.57968000
H -3.32679000 -2.46107000 -1.44983000
H -0.94209000 -2.15306000 -1.12869000
H -5.97198000 -0.90580000 2.18253000
H -8.34434000 -1.26407000 1.91282000
H -9.26240000 -2.50178000 -0.06982000
H -7.63806000 -3.37920000 -1.77023000
H -5.25798000 -3.06873000 -1.51271000
C 2.32798000 0.56276000 0.74525000
C 3.14409000 -0.64894000 1.22539000
C 2.49538000 -1.29493000 2.46371000
C 0.95405000 -1.19003000 2.45442000
C 0.44023000 -1.18585000 1.00607000
C 0.89635000 0.13018000 0.31945000
H 2.23755000 1.24048000 1.60426000
H 4.17184000 -0.34247000 1.44840000
H 3.21508000 -1.37812000 0.40891000
H 2.79317000 -2.34859000 2.51161000
H 2.88750000 -0.82228000 3.37161000
H 0.64954000 -0.26026000 2.95605000
H 0.52972000 -2.01873000 3.03046000
H 0.95180000 -2.01863000 0.48928000
H 0.84777000 0.00310000 -0.76789000
H 0.20224000 0.94114000 0.56352000
C 5.43790000 5.25355000 -1.94193000
C 5.64548000 4.63013000 -3.19452000
C 5.16854000 3.36453000 -3.42033000
C 4.46393000 2.66271000 -2.40928000
C 4.25120000 3.28906000 -1.15122000
C 4.75746000 4.59930000 -0.94725000
C 3.95839000 1.35053000 -2.60502000
C 3.28103000 0.70388000 -1.60857000
C 3.05532000 1.31836000 -0.34497000
C 3.54208000 2.58620000 -0.14148000
H 5.81806000 6.25633000 -1.77219000
H 6.18181000 5.15878000 -3.97642000
H 5.32100000 2.88069000 -4.38152000
H 4.59600000 5.07771000 0.01512000
H 4.11384000 0.86582000 -3.56523000
H 2.90138000 -0.29899000 -1.78267000
H 3.38478000 3.07583000 0.81721000
$end
$rem
JOB_TYPE Optimization
METHOD wB97X-D
BASIS aug-cc-pVDZ
SCF_CONVERGENCE 8
SCF_MAX_CYCLES 500
GEOM_OPT_MAX_CYCLES 200
SYMMETRY FALSE
SYM_IGNORE TRUE
GUI 2
CDFT TRUE
CDFT_PRINT TRUE
CDFT_BECKE_POP TRUE
BECKE_SHIFT UNSHIFTED
XC_GRID 2
MEM_TOTAL 248000
MEM_STATIC 4000
$end
$cdft
1.0
1 1 21
1.0
1 1 21 s
$end
@@@
$molecule
read
$end
$rem
JOB_TYPE Freq
METHOD wB97X-D
BASIS aug-cc-pVDZ
SCF_CONVERGENCE 8
SYMMETRY FALSE
SYM_IGNORE TRUE
SCF_GUESS READ
CDFT TRUE
CDFT_PRINT TRUE
CDFT_BECKE_POP TRUE
BECKE_SHIFT UNSHIFTED
XC_GRID 2
MEM_TOTAL 248000
MEM_STATIC 4000
$end
$cdft
1.0
1 1 21
1.0
1 1 21 s
$end