SCF convergence problem

Hello. Recently, I have been trying to execute geometry optimizations for the S0, S1, and T1 state using Q-Chem 6.0.

At the 0th geometry optimization step, when the SCF cycles were proceeded, the calculated energies oscillated, so finally, it wasn’t converged.

Before trying to resolve this issue, I wonder which options can be edited.

I saw that change of SCF algorithm, adding a level shifting, or setting a electronic temperature (smearing) may be helpful for treating this situation.

Without them, are there any possible factors affecting SCF convergence?

Here are my input file and the problematic parts in output file, and any advice are surely meaningful for me, so thank you in advance.

cf. I already tested the default SCF algorithm (DIIS), but it failed, so I tried RCA_DIIS but it still indicated a problem.

$molecule
0 1
C         -0.23056       -0.00628        0.19338
C         -1.23784       -0.70743       -0.37285
C         -1.25478       -2.02365        0.10200
C          0.45059       -0.96012        1.05207
C         -0.26412       -2.19992        0.97053
C          1.66369       -0.88508        1.83428
C          2.06604       -1.98967        2.51055
C          1.32076       -3.22409        2.52360
C          0.17975       -3.35478        1.78694
C         -2.20857       -0.27381       -1.28802
C         -3.18581       -1.18590       -1.71801
C         -3.19275       -2.50914       -1.23701
C         -2.22212       -2.93969       -0.31798
C          0.02537        1.46323        0.08795
C         -1.12786        2.31414        0.59479
C         -1.10549        3.60938       -0.21521
C         -0.33692        3.21280       -1.41952
C          0.41500        2.07198       -1.20113
C         -0.27372        3.91704       -2.61766
C          0.53291        3.42527       -3.64759
C          1.36448        2.30751       -3.42997
C          1.36663        1.65390       -2.16660
C          2.20444        1.85211       -4.45570
C          3.16240        0.86153       -4.20561
C          3.30903        0.34776       -2.89788
C          2.35683        0.68212       -1.90524
C         -1.16303        2.50270        2.10834
C          4.00206        0.40779       -5.23740
C          5.07927       -0.44666       -4.95838
C          5.36190       -0.78642       -3.61777
C          4.43669       -0.44766       -2.60434
C          3.27438       -1.92028        3.18265
C          3.78187       -3.02584        3.85395
C          3.05512       -4.23127        3.95963
C          1.81036       -4.31800        3.29243
C          5.89093       -0.94936       -5.99318
C          7.45311       -1.83041       -4.35337
C          7.05124       -1.68692       -5.69871
C          6.57681       -1.43494       -3.32049
C          5.06486       -2.93817        4.34747
C          5.67351       -4.04680        4.90976
C          4.97333       -5.25219        5.13629
C          3.63079       -5.33060        4.66948
C          8.72259       -2.36775       -4.06976
C          9.53407       -2.87922       -5.10129
C          9.02553       -2.94401       -6.41597
C          7.81597       -2.28799       -6.71932
C         10.82888       -3.36061       -4.83398
C          9.72013       -3.69641       -7.38605
C         10.94169       -4.32488       -7.06187
C         11.55279       -4.05615       -5.81903
C          7.02933       -3.97040        5.10866
C          7.73300       -5.10487        5.45438
C          7.09668       -6.30322        5.84525
C          5.67552       -6.36054        5.71646
C          9.07749       -5.07068        5.19701
C          9.78551       -6.24885        5.22545
C          9.29590       -7.42358        5.83206
C          7.91301       -7.43499        6.19418
C         10.87657       -6.29409        4.40223
C         11.44480       -7.51570        4.13958
C         11.25674       -8.63706        4.96531
C         10.15039       -8.58248        5.86950
H          2.23936        0.03722        1.82898
H         -0.38049       -4.28561        1.76539
H         -2.21844        0.73758       -1.67200
H         -3.94221       -0.86762       -2.42439
H         -3.95529       -3.19827       -1.57691
H         -2.23417       -3.95608        0.05373
H         -2.07320        1.80489        0.31543
H         -2.13437        3.98226       -0.40604
H         -0.49753        4.39535        0.28742
H         -0.86153        4.81510       -2.75982
H          0.55437        3.95317       -4.59342
H          2.15426        2.31225       -5.43683
H          2.43620        0.24842       -0.91615
H         -0.24031        3.00240        2.46654
H         -1.25414        1.51028        2.60190
H         -2.04822        3.11217        2.39095
H          3.84092        0.75068       -6.25373
H          4.61347       -0.76904       -1.58392
H          3.86277       -1.00772        3.13123
H          1.25766       -5.25109        3.31843
H          5.62565       -0.75667       -7.02691
H          6.84559       -1.62099       -2.28671
H          5.63483       -2.02633        4.18894
H          3.08454       -6.26260        4.75850
H          9.07147       -2.40697       -3.04405
H          7.45889       -2.26267       -7.74297
H         11.24855       -3.25142       -3.84057
H          9.27767       -3.84430       -8.36510
H          7.55832       -3.06508        4.81908
H          5.15827       -7.29455        5.90197
H          9.50955       -4.18119        4.74205
H          7.45738       -8.36286        6.51844
H         11.10734       -5.43581        3.77382
H          9.84309       -9.48850        6.37704
C         11.99500       -7.67112        2.89720
C         12.42820       -8.91329        2.50355
C         12.70294       -9.92476        3.43414
C         12.06850       -9.79856        4.71123
C         12.45072       -9.19401        1.16192
C         12.94977      -10.39307        0.71134
C         13.72194      -11.19138        1.56524
C         13.51274      -11.01891        2.97378
C         12.70781      -10.77285       -0.59104
C         13.47742      -11.74934       -1.18244
C         14.62152      -12.19544       -0.50572
C         14.65449      -12.06837        0.92412
C         15.71926      -12.57811       -1.32777
C         15.55724      -12.46248       -2.74908
C         13.21547      -12.08359       -2.50312
C         14.26808      -12.46805       -3.30970
C         12.83980       -4.55818       -5.54446
C         11.52419       -5.28260       -7.91570
C         12.70657       -5.94975       -7.52553
C         13.42955       -5.50496       -6.39902
C         14.65642       -6.11088       -6.04976
C         15.01521       -7.33750       -6.63402
C         13.09610       -7.14458       -8.15335
C         14.15579       -7.89712       -7.60246
C         16.08596       -8.08893       -6.08599
C         16.04687       -9.48989       -6.21071
C         15.01726      -10.05468       -6.99347
C         14.21111       -9.27301       -7.84374
C         16.81776      -10.28783       -5.31478
C         16.21574      -11.47851       -4.85590
C         14.55935      -11.33195       -6.68765
C         15.00628      -11.86633       -5.46951
C         16.60848      -12.02207       -3.59003
C         14.02874      -12.45674       -4.68508
H         11.91252       -6.86655        2.17027
H         12.06060      -10.64883        5.38146
H         12.02460       -8.48589        0.45705
H         13.91907      -11.73702        3.67469
H         11.98175      -10.22964       -1.18808
H         15.43779      -12.52984        1.51202
H         16.69455      -12.66290       -0.86522
H         12.27743      -11.78938       -2.96467
H         13.32716       -4.31035       -4.60885
H         10.99154       -5.59169       -8.80865
H         15.21780       -5.74639       -5.19792
H         12.45268       -7.57216       -8.91530
H         16.74123       -7.64600       -5.34603
H         13.42567       -9.72620       -8.44073
H         17.60458       -9.84536       -4.71635
H         13.62227      -11.65757       -7.13060
H         17.54565      -11.74997       -3.12053
H         13.01229      -12.49210       -5.06769
$end

$rem
JOBTYPE = OPTIMIZATION
EXCHANGE = CAM-B3LYP
BASIS = 6-31G**
GEOM_OPT_MAX_CYCLES = 1500
GEOM_OPT_DMAX = 300
GEOM_OPT_TOL_DISPLACEMENT = 1200
GEOM_OPT_TOL_ENERGY = 100
GEOM_OPT_TOL_GRADIENT = 300
SCF_CONVERGENCE = 8
SCF_MAX_CYCLES = 999
SCF_ALGORITHM = RCA_DIIS
DFT_D = D3_BJ
MEM_TOTAL = 48000
MEM_STATIC = 6000
THRESH = 14
$end

 ---------------------------------------
  Cycle       Energy         DIIS Error
 ---------------------------------------
    1   -3760.8587390770      1.95E-02
    2   -3724.7707511166      1.13E-03
    3   -3724.9844776649      5.02E-04 Done RCA. Switching to DIIS
    4   -3724.7692555165      9.39E-04
    5   -3725.2092364505      4.82E-04
    6   -3725.3347576467      2.35E-04
    7   -3725.3609983820      1.59E-04
    8   -3725.3798595956      7.31E-05
    9   -3725.3861901980      4.02E-05
   10   -3725.3909905749      3.46E-05
   11   -3725.3950685357      2.99E-05
   12   -3725.3983866874      2.54E-05
   13   -3725.4030237856      2.03E-05
   14   -3725.4059160820      1.48E-05
   15   -3725.4066837571      9.95E-06
   16   -3725.4071780589      7.60E-06
   17   -3725.4075881675      8.61E-06
   18   -3725.4076386770      8.20E-06
   19   -3725.4077323224      9.12E-06
   20   -3725.4073923162      9.63E-06
   21   -3725.4063830699      8.54E-06
   22   -3725.4062511469      8.96E-06
   23   -3725.4060875750      9.49E-06
   24   -3725.4060555864      8.80E-06
   25   -3725.4057481830      1.02E-05
   26   -3725.4064817298      8.42E-06
   27   -3725.4073276588      1.40E-05
   28   -3725.4069168300      1.35E-05
   29   -3725.4066047571      1.33E-05
   30   -3725.4062237633      1.43E-05
   31   -3725.4059567946      1.55E-05
   32   -3725.4058530246      1.58E-05
   33   -3725.4059194997      1.60E-05
   34   -3725.4062066535      1.58E-05
   35   -3725.4073641563      2.34E-05
   36   -3725.4070821574      1.91E-05
   37   -3725.4069866190      1.47E-05
   38   -3725.4067127709      9.05E-06
   39   -3725.4064438257      7.88E-06
   40   -3725.4065337798      8.34E-06
   41   -3725.4063350518      7.24E-06
   42   -3725.4069046155      6.14E-06
   43   -3725.4072258153      1.01E-05
   44   -3725.4079718671      1.68E-05
   45   -3725.4072360606      8.12E-06
   46   -3725.4074692614      1.27E-05
   47   -3725.4066377514      8.47E-06
   48   -3725.4062282952      1.01E-05
   49   -3725.4058734940      1.07E-05
   50   -3725.4060449985      1.04E-05
   51   -3725.4072773450      1.35E-05
   52   -3725.4074874020      1.47E-05
   53   -3725.4069999440      1.21E-05
   54   -3725.4073041051      1.25E-05
   55   -3725.4073585874      1.15E-05
   56   -3725.4075781751      1.49E-05
   57   -3725.4078474117      2.39E-05
   58   -3725.4075575137      2.02E-05
   59   -3725.4072060804      1.86E-05
   60   -3725.4065220384      1.50E-05
   61   -3725.4077565985      2.23E-05
   62   -3725.4069925088      1.59E-05
   63   -3725.4069898639      1.68E-05
   64   -3725.4054931341      1.65E-05
   65   -3725.4053686638      1.82E-05
   66   -3725.4062913675      1.59E-05
   67   -3725.4063429723      1.97E-05
   68   -3725.4068175860      2.11E-05
   69   -3725.4064881730      2.20E-05
   70   -3725.4066114809      2.22E-05
   71   -3725.4065661211      2.33E-05
   72   -3725.4062934770      2.34E-05
   73   -3725.4066441454      1.88E-05
   74   -3725.4072531028      1.86E-05
   75   -3725.4073340927      1.81E-05
   76   -3725.4073872054      1.87E-05
   77   -3725.4073823422      2.03E-05
   78   -3725.4070434113      2.16E-05
   79   -3725.4062438050      2.10E-05
   80   -3725.4061731234      1.22E-05
   81   -3725.4061129662      7.48E-06
   82   -3725.4062724934      6.20E-06
   83   -3725.4061695110      7.32E-06
   84   -3725.4063118600      1.99E-05
   85   -3725.4064710432      9.14E-06
   86   -3725.4065765976      9.44E-06
   87   -3725.4068184183      8.43E-06
   88   -3725.4068982848      8.33E-06
   89   -3725.4069040085      8.34E-06
   90   -3725.4070781266      7.80E-06
   91   -3725.4072183857      8.61E-06
   92   -3725.4073462009      8.23E-06
   93   -3725.4059649599      5.85E-06
   94   -3725.4039706777      1.24E-05
   95   -3725.4051309387      9.52E-06
   96   -3725.4053661610      9.07E-06
   97   -3725.4053887527      9.51E-06
   98   -3725.4053888248      9.50E-06
   99   -3725.4053317826      9.88E-06
  100   -3725.4052882979      1.02E-05
  101   -3725.4052932432      1.01E-05
  102   -3725.4052386721      1.04E-05
  103   -3725.4054160401      2.91E-05
  104   -3725.4057178423      1.31E-05
  105   -3725.4059151598      1.40E-05
  106   -3725.4061921864      1.11E-05
  107   -3725.4064714218      9.59E-06
  108   -3725.4073165841      5.60E-06
  109   -3725.4078049596      5.89E-06
  110   -3725.4072361390      4.90E-06
  111   -3725.4057453234      1.21E-05
  112   -3725.4051057117      1.42E-05
  113   -3725.4054199609      1.32E-05
  114   -3725.4056636275      1.17E-05
  115   -3725.4059688964      1.09E-05
  116   -3725.4060591717      1.05E-05
  117   -3725.4057996385      1.19E-05
  118   -3725.4055315233      1.34E-05
  119   -3725.4054716948      1.33E-05
  120   -3725.4064081892      1.40E-05
  121   -3725.4063620559      3.25E-05
  122   -3725.4067913014      9.16E-06
  123   -3725.4068864641      9.39E-06
  124   -3725.4069833700      8.95E-06
  125   -3725.4069014302      8.92E-06
  126   -3725.4064203117      7.30E-06
  127   -3725.4060384384      6.63E-06
  128   -3725.4075789698      1.06E-05
  129   -3725.4088677529      4.11E-05
  130   -3725.4091458978      4.46E-05
  131   -3725.4091661926      3.00E-05
  132   -3725.4080111169      2.54E-05
  133   -3725.4072670939      2.54E-05
  134   -3725.4072577820      2.54E-05
  135   -3725.4071949833      2.82E-05
  136   -3725.4071505781      2.66E-05
  137   -3725.4071110323      2.37E-05
  138   -3725.4067790415      2.62E-05
  139   -3725.4065250900      2.79E-05
  140   -3725.4066700819      2.55E-05
  141   -3725.4057920144      2.31E-05
  142   -3725.4049780957      1.95E-05
  143   -3725.4046608789      5.17E-05
  144   -3725.4056971793      1.50E-05
  145   -3725.4058357384      1.50E-05
  146   -3725.4061602598      1.18E-05
  147   -3725.4063778914      1.05E-05
  148   -3725.4069326095      8.37E-06
  149   -3725.4075043764      5.65E-06
  150   -3725.4069410744      6.00E-06
  151   -3725.4058704550      6.67E-06
  152   -3725.4051811076      8.89E-06
  153   -3725.4066167011      8.97E-06
  154   -3725.4068659860      1.34E-05
  155   -3725.4068305694      1.35E-05
  156   -3725.4069512183      1.28E-05
  157   -3725.4070132909      1.25E-05
  158   -3725.4069867239      1.16E-05
  159   -3725.4064624699      1.27E-05
  160   -3725.4064847548      1.25E-05
  161   -3725.4063605324      1.26E-05
  162   -3725.4063903171      1.23E-05
  163   -3725.4065721283      1.21E-05
  164   -3725.4066651827      1.15E-05
  165   -3725.4083134878      2.63E-05
  166   -3725.4086055266      4.22E-05
  167   -3725.4096631687      8.36E-06
  168   -3725.4099485792      7.81E-06
  169   -3725.4092721258      7.15E-06
  170   -3725.4071278576      1.94E-05
  171   -3725.4068955081      1.99E-05
  172   -3725.4073416351      1.96E-05
  173   -3725.4079998976      2.36E-05
  174   -3725.4069968285      2.11E-05
  175   -3725.4059994256      2.78E-05
  176   -3725.4063700724      2.31E-05
  177   -3725.4064162984      2.04E-05
  178   -3725.4062604550      2.05E-05
  179   -3725.4063150234      2.04E-05
  180   -3725.4064614916      2.04E-05
  181   -3725.4064916845      1.89E-05
  182   -3725.4063384793      2.05E-05
  183   -3725.4063655354      2.06E-05
  184   -3725.4066428241      1.93E-05
  185   -3725.4073421032      1.60E-05
  186   -3725.4069901753      1.52E-05
  187   -3725.4068700697      1.55E-05
  188   -3725.4076230649      1.09E-05
  189   -3725.4080430675      1.26E-05
  190   -3725.4070047790      9.98E-06
  191   -3725.4065828509      1.49E-05
  192   -3725.4061094240      1.59E-05
  193   -3725.4060656106      1.75E-05
  194   -3725.4064466086      1.92E-05
  195   -3725.4068992049      2.05E-05
  196   -3725.4071367803      2.27E-05
  197   -3725.4074065751      2.44E-05
  198   -3725.4073302956      2.19E-05
  199   -3725.4067534152      2.12E-05
  200   -3725.4067194653      2.22E-05
  201   -3725.4073309423      2.55E-05
  202   -3725.4070634619      2.40E-05
  203   -3725.4088316127      3.96E-05
  204   -3725.4085143648      5.18E-05
  205   -3725.4080289547      3.10E-05
  206   -3725.4072419018      4.09E-05
  207   -3725.4067404873      2.24E-05
  208   -3725.4071230250      4.02E-05
  209   -3725.4070022627      1.63E-05
  210   -3725.4070772322      7.73E-06
  211   -3725.4069432041      6.94E-06
  212   -3725.4068445169      6.60E-06
  213   -3725.4067549663      5.44E-06
  214   -3725.4066720324      5.79E-06
  215   -3725.4067178479      5.64E-06
  216   -3725.4068864532      5.52E-06
  217   -3725.4069047020      7.18E-06
  218   -3725.4069876049      8.39E-06
  219   -3725.4070453150      1.71E-05
  220   -3725.4073091153      1.01E-05
  221   -3725.4070300002      1.07E-05
  222   -3725.4062672515      9.03E-06
  223   -3725.4060040434      8.48E-06
  224   -3725.4057848553      8.21E-06
  225   -3725.4073065381      6.16E-06
  226   -3725.4067761579      7.25E-06
  227   -3725.4081151239      4.70E-05
  228   -3725.4086322094      6.04E-05
  229   -3725.4091120447      7.53E-05
  230   -3725.4094767315      6.17E-05
  231   -3725.4095013216      6.69E-05
  232   -3725.4093735180      6.94E-05
  233   -3725.4095467105      5.81E-05
  234   -3725.4094538767      6.63E-05
  235   -3725.4094580536      6.90E-05
  236   -3725.4090455452      2.01E-05
  237   -3725.4073476468      1.22E-05
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  243   -3725.4075815747      1.21E-05
  244   -3725.4074411175      1.23E-05
  245   -3725.4073726805      1.09E-05
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  249   -3725.4076041684      1.06E-05
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  252   -3725.4086802041      4.32E-05
  253   -3725.4077821637      7.40E-06
  254   -3725.4076881900      8.18E-06
  255   -3725.4071102890      6.11E-06
  256   -3725.4069281251      5.57E-06
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  273   -3725.4056075797      8.51E-06
  274   -3725.4063516413      1.34E-05
  275   -3725.4060468841      1.62E-05
  276   -3725.4075012589      1.98E-05
  277   -3725.4077985814      3.97E-05
  278   -3725.4079914293      6.23E-05
  279   -3725.4080172841      2.31E-05
  280   -3725.4090560230      1.77E-05
  281   -3725.4091739996      2.15E-05
  282   -3725.4097666800      3.61E-05
  283   -3725.4099987086      3.02E-05
  284   -3725.4072002879      2.19E-05
  285   -3725.4057796741      2.87E-05
  286   -3725.4053234497      3.97E-05
  287   -3725.4061500852      2.32E-05
  288   -3725.4058400923      3.75E-05
  289   -3725.4076238837      4.70E-05
  290   -3725.4074155735      4.49E-05
  291   -3725.4067942402      3.01E-05
  292   -3725.4059562137      3.64E-05
  293   -3725.4062943715      2.53E-05
  294   -3725.4060867081      2.51E-05
  295   -3725.4057249134      2.52E-05
  296   -3725.4058846800      2.50E-05
  297   -3725.4061956197      1.86E-05
  298   -3725.4072537036      1.48E-05
  299   -3725.4075303893      1.52E-05
  300   -3725.4064533639      1.69E-05
  301   -3725.4060907850      2.01E-05
  302   -3725.4064518483      2.22E-05
  303   -3725.4061816495      2.43E-05
  304   -3725.4064278430      2.09E-05
  305   -3725.4064591603      1.98E-05
  306   -3725.4072178381      1.11E-05
  307   -3725.4065220665      1.30E-05
  308   -3725.4065668445      1.19E-05
  309   -3725.4065722078      1.17E-05
  310   -3725.4066930745      5.51E-06
  311   -3725.4073523423      5.21E-06
  312   -3725.4075494304      6.30E-06
  313   -3725.4073787532      7.54E-06
  314   -3725.4082784733      1.24E-05
  315   -3725.4075653791      1.06E-05
  316   -3725.4076426880      1.50E-05
  317   -3725.4065713395      1.80E-05
  318   -3725.4058765777      1.75E-05
  319   -3725.4059085359      1.63E-05
  320   -3725.4057566070      1.82E-05
  321   -3725.4057738100      1.79E-05
  322   -3725.4057223887      1.81E-05
  323   -3725.4056698864      1.88E-05
  324   -3725.4056972985      2.02E-05
  325   -3725.4057537599      2.02E-05
  326   -3725.4060594119      1.73E-05
  327   -3725.4062132119      1.68E-05
  328   -3725.4064522343      1.56E-05
  329   -3725.4082516909      1.80E-05
  330   -3725.4098370624      5.44E-05
  331   -3725.4084017942      2.86E-05
  332   -3725.4079310434      1.53E-05
  333   -3725.4078032419      6.70E-06
  334   -3725.4076263804      8.03E-06
  335   -3725.4074071212      7.33E-06
  336   -3725.4064393046      6.13E-06
  337   -3725.4064738359      5.93E-06
  338   -3725.4070590782      5.96E-06
  339   -3725.4069668873      5.64E-06
  340   -3725.4068361515      5.32E-06
  341   -3725.4070028264      1.20E-05
  342   -3725.4070699714      1.11E-05
  343   -3725.4069192304      1.37E-05
  344   -3725.4064015540      2.83E-05
  345   -3725.4052036726      1.40E-05
  346   -3725.4060482551      7.84E-06
  347   -3725.4070702837      1.90E-05
  348   -3725.4080731180      3.27E-05
  349   -3725.4085414139      3.41E-05
  350   -3725.4094063431      4.46E-05
  351   -3725.4090299922      3.45E-05
  352   -3725.4092958687      4.44E-05
  353   -3725.4087451447      2.37E-05
  354   -3725.4087258598      2.48E-05
  355   -3725.4089161253      2.67E-05
  356   -3725.4089900275      2.78E-05
  357   -3725.4088418189      2.69E-05
  358   -3725.4088419338      2.84E-05
  359   -3725.4074531652      1.54E-05
  360   -3725.4076440342      2.91E-05
  361   -3725.4080882603      7.93E-06
  362   -3725.4082657280      8.04E-06
  363   -3725.4079526562      7.87E-06
  364   -3725.4069528452      5.10E-06
  365   -3725.4067462603      4.67E-06
  366   -3725.4066353229      4.71E-06
  367   -3725.4071665925      5.29E-06
  368   -3725.4080065463      1.12E-05
  369   -3725.4070112976      1.88E-05
  370   -3725.4060120336      2.19E-05
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  376   -3725.4065468330      1.71E-05
  377   -3725.4065501825      1.71E-05
  378   -3725.4065288453      1.69E-05
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  380   -3725.4070069520      8.98E-06
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  383   -3725.4071394665      8.60E-06
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  410   -3725.4079940766      1.70E-05
  411   -3725.4076297548      1.77E-05
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  413   -3725.4069735075      2.28E-05
  414   -3725.4071015924      2.15E-05
  415   -3725.4066695267      2.10E-05
  416   -3725.4059084816      2.61E-05
  417   -3725.4056647123      2.94E-05
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  423   -3725.4060241331      2.55E-05
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  426   -3725.4073488782      6.46E-06
  427   -3725.4078083644      1.15E-05
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  444   -3725.4089598912      4.74E-05
  445   -3725.4081945949      2.59E-05
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  447   -3725.4077953260      3.38E-05
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  451   -3725.4073961841      4.36E-05
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  455   -3725.4059056191      3.67E-05
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  457   -3725.4064162686      2.80E-05
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  464   -3725.4078508845      1.00E-05
  465   -3725.4081355615      1.15E-05
  466   -3725.4086057837      9.44E-06
  467   -3725.4086061847      7.30E-06
  468   -3725.4079633325      5.36E-06
  469   -3725.4072832817      8.04E-06
  470   -3725.4057930949      2.13E-05
  471   -3725.4057954781      2.12E-05
  472   -3725.4059024889      2.06E-05
  473   -3725.4059526913      2.07E-05
  474   -3725.4059639582      2.10E-05
  475   -3725.4060295265      2.12E-05
  476   -3725.4061109918      2.09E-05
  477   -3725.4062614906      1.99E-05
  478   -3725.4062115895      2.01E-05
  479   -3725.4063543498      1.91E-05
  480   -3725.4063706340      1.86E-05
  481   -3725.4064699668      1.82E-05
  482   -3725.4063283632      1.87E-05
  483   -3725.4092719427      2.81E-05
  484   -3725.4079384696      2.11E-05
  485   -3725.4070764922      2.22E-05
  486   -3725.4060094389      3.23E-05
  487   -3725.4061523654      3.02E-05
  488   -3725.4064711104      2.74E-05
  489   -3725.4069795189      2.36E-05
  490   -3725.4068648131      2.70E-05
  491   -3725.4068161378      2.80E-05
  492   -3725.4067417685      2.92E-05
  493   -3725.4066605739      2.88E-05
  494   -3725.4068384129      2.63E-05
  495   -3725.4068285452      2.83E-05
  496   -3725.4068510190      2.83E-05
  497   -3725.4069947885      2.15E-05
  498   -3725.4070044757      1.86E-05
  499   -3725.4084616573      9.56E-06
  500   -3725.4073011099      8.44E-06
.
.
.
  990   -3725.4080741057      1.49E-05
  991   -3725.4080733428      1.09E-05
  992   -3725.4078998654      8.22E-06
  993   -3725.4074168445      1.03E-05
  994   -3725.4072071266      1.16E-05
  995   -3725.4072946317      1.05E-05
  996   -3725.4075631950      8.01E-06
  997   -3725.4077429180      8.70E-06
  998   -3725.4077689662      8.51E-06
  999   -3725.4074125517      7.40E-06    Convergence failure

 Q-Chem fatal error occurred in module scfman/scfman.C, line 5600:

 SCF failed to converge


 Please submit a crash report at q-chem.com/reporter 

If the DIIS error is oscillating in the regime of 10^-6 or so, you may consider turning INCFOCK off. In addition, the following worked for me with DIIS_GDM algorithm and THRESH_DIIS_SWITCH = 5:

$rem
JOBTYPE = SP
EXCHANGE = CAM-B3LYP
BASIS = 6-31G**
!GEOM_OPT_MAX_CYCLES = 1500
!GEOM_OPT_DMAX = 300
!GEOM_OPT_TOL_DISPLACEMENT = 1200
!GEOM_OPT_TOL_ENERGY = 100
!GEOM_OPT_TOL_GRADIENT = 300
SCF_CONVERGENCE = 8
SCF_MAX_CYCLES = 999
SCF_ALGORITHM = DIIS_GDM
THRESH_DIIS_SWITCH = 5
INCFOCK = 0
DFT_D = D3_BJ
MEM_TOTAL = 48000
MEM_STATIC = 6000
THRESH = 14
$end

Starting v6.3.0, you can try using our new, black-box robust SCF procedure using the SCF_ALGORITHM = ROBUST setting, which might help with many similarly difficult-to-converge SCF calculations. Hope that helps.

For a molecule of that size, and given that you are having problems, I would set THRESH = 14 just to be sure.

Thank you for your comment. I’ll try your suggestion of INCFOCK and DIIS_GDM algorithm.

I have some questions for your answers.

  1. What is the role of INCFOCK option here?

  2. Actually, I heard that GDM should not be utilized in TDDFT which calculates the excited state in somewhere. Is it right? Or doesn’t the SCF algorithm matter for this problem?

INCFOCK is incremental Fock build; please see the manual for a description. (I suggest downloading the PDF manual that is globally searchable, unlike the HTML version.) There is no reason to avoid any particular SCF convergence algorithm for TDDFT, which is calculated at the end using the reference state converged by the SCF procedure.