Is it possible to read in transition structure coordinates and hessians for a IRC calculation from separate TS and frequency calculations?
You should start from a transition state. Reading the Hessian is not required. See the sample job here:
https://manual.q-chem.com/latest/Ch9.S7.SS1.html
Thanks for your reply.
However, I have a huge system that took around 3 days to calculate the frequencies on 16 cores and 200 GB memory. I already have the complete Hessian and would prefer to read it into my IRC calculation. Is that possible?
The input file is attached for reference.
$molecule
0 2
C -0.8914619001 1.8093202059 -1.3012723601
C -0.4797615186 2.6063608008 -0.2011505855
C -1.2469125722 3.6601308138 0.2003667581
C -2.4698260843 3.9723758340 -0.4503304739
C -2.8529781782 3.2073766239 -1.5821191579
C -2.0290292363 2.1336381769 -1.9998746695
C -4.0671500529 3.5147297028 -2.2434340300
C -4.8698532583 4.5248224043 -1.7891861762
C -4.4954609689 5.2776204269 -0.6542110038
C -3.3216979253 5.0102116212 -0.0026038877
H 0.4411475904 2.3715170489 0.3112311317
H -0.9333654961 4.2640808768 1.0466284177
H -2.3309745372 1.5394480346 -2.8561133422
H -4.3590280745 2.9247334245 -3.1065601180
H -5.8030725979 4.7470145208 -2.2953300755
H -5.1458771961 6.0700615228 -0.2998958121
H -3.0332418911 5.5869121455 0.8707865989
S -0.1436888594 0.2623323159 -1.6987450557
Cl 2.0222654384 0.6691471772 -1.6009785283
B -0.5968422543 -1.4774134665 0.7329782459
C -1.1718630059 -2.6264639833 -0.1903111759
C -2.3884326619 -3.2461701501 0.0764487600
F -3.1082008166 -2.8867281483 1.1428232315
C -2.9074891425 -4.2570464344 -0.7145633952
F -4.0730640692 -4.8211349247 -0.4176662322
C -2.1977560707 -4.6810394854 -1.8259043762
F -2.6822934385 -5.6425680557 -2.5970394506
C -0.9751799364 -4.1002967475 -2.1243913870
F -0.2875439818 -4.5106324571 -3.1839683837
C -0.4813372909 -3.1074666970 -1.2988868943
F 0.7165747562 -2.6048327293 -1.6171452256
C -1.5831861395 -0.3956416265 1.3161692981
C -2.6972959182 0.0421173006 0.5944192944
F -2.9800438004 -0.4841487858 -0.6001922128
C -3.5428230698 1.0439639130 1.0315328648
F -4.5814784241 1.4253269292 0.2997135903
C -3.2908850253 1.6563253833 2.2474633393
F -4.0723542852 2.6353562141 2.6738574221
C -2.2247052464 1.2303376012 3.0220849053
F -1.9999883743 1.7947273132 4.2047219665
C -1.4088138219 0.2124204307 2.5592279351
F -0.4352326439 -0.1855040152 3.3801555967
C 0.9081829103 -1.5958721798 1.2074881080
C 1.7064379594 -0.4969571491 1.5248237339
F 1.2053782075 0.7374202532 1.4926321210
C 3.0366867206 -0.5972165362 1.8857133061
F 3.7487812861 0.4887130538 2.1716578952
C 3.6297046891 -1.8445871190 1.9498371536
F 4.9126475980 -1.9585604039 2.2575081754
C 2.8775502495 -2.9721479749 1.6728995052
F 3.4441451946 -4.1724957952 1.7318044002
C 1.5466133429 -2.8342768168 1.3181648730
F 0.8839474108 -3.9712243544 1.0999424606
C 1.5466133429 -2.8342768168 1.3181648730
F 0.8839474108 -3.9712243544 1.0999424606
C 4.9540809176 -0.2867883103 -1.0764402139
C 4.3330898708 0.8606672472 -1.1752525645
C 4.5332595206 2.2705646689 -1.1286303374
C 4.1419935133 3.0201125021 -0.0052841764
H 3.7000308813 2.5112460058 0.8425023204
C 4.3226059614 4.3919763829 0.0108557404
H 4.0257620244 4.9630521118 0.8839699688
C 4.8813620533 5.0406577491 -1.0881852455
H 5.0179320133 6.1166837675 -1.0706620292
C 5.2586128440 4.3097119960 -2.2110332582
H 5.6905467388 4.8132170222 -3.0690543292
C 5.0797435183 2.9367413814 -2.2392109774
H 5.3596044727 2.3603732081 -3.1140452592
H 6.0125775536 -0.2157499987 -0.8065025275
C 4.4260634219 -1.6718792387 -1.3075202924
H 4.7758451196 -2.3512358827 -0.5267134580
H 3.3378415997 -1.6957194367 -1.3396789449
H 4.8029060171 -2.0610273422 -2.2581873247
$end
$rem
BASIS = 6-311G*
GUI = 2
JOB_TYPE = freq
METHOD = WB97X-D
SCF_CONVERGENCE = 8
! SCF_MAX_CYCLES = 250
! GEOM_OPT_MAX_CYCLES = 250
! GEOM_OPT_DMAX = 10
GEOM_OPT_DRIVER = optimize
CPSCF_NSEG = 3
MEM_TOTAL = 200000
$end
I do not see anything in the manual to indicate this, but the IRC calculation does not seem to begin with a Hessian calculation so I think you just need to use the starting structure.