transition state OPT job converged but has 2 imaginary frequencies

ABQTrap · 2024-11-22 14:07:25

Dear all,

I tried to optimize the transition state by CASPT2/CASSCF, the job ended successfully, and the four convergence criteira were met. However the output file showed that the optimized structrue has two negative frequencies, both are around ~200 cm-1. one is what I expected, while the other is the rotation of the methyl group. I expected the OpenMolcas would continue the optimization since two negative frequencies were found. With two negative frequencies, the optimized structure may not be the true transition state. So how to make the OpenMolcas to found the true transition state in my condition? Thank a lot.

&GATEWAY
 coord=TS-guess.xyz
 basis=DEF2-TZVPP

>>> COPY $MOLCAS/CAS87/TS-guess.RasOrb INPORB

>>> Do While  

&SEWARD

&RASSCF
 LUMOrb
 nactel = 8 0 0
 inactive= 31  
 ras2 = 7        
 spin = 1
 ciroot = 1 1 1

&CASPT2
 rlxroot = 1
 MAXIter = 100
 imaginary = 0.1

&MCLR

&ALASKA

&SLAPAF
 Hupdate = TS-BFGS
 MAXStep = 0.1
 FindTS
 TSConstraints
    d1 = Bond N2 N7
 Value
    d1 = 2.6 angstrom
 End of TSConstraints

>>> EndDo

**********************************************************************************************************************
*                                    Energy Statistics for Geometry Optimization                                     *
**********************************************************************************************************************
                       Energy     Grad      Grad              Step                 Estimated   Geom       Hessian     
Iter      Energy       Change     Norm      Max    Element    Max     Element     Final Energy Update Update   Index  
  1   -436.03832683  0.00000000 0.027919 -0.012404 nrc016  -0.060012* nrc006     -436.04002450 RS-RFO  None      0    
  2   -436.03678731  0.00153952 0.011076  0.003563 nrc034   0.141499* nrc001     -436.03696855 RS-RFO TSBFGS     0    
  3   -436.03439837  0.00238894 0.031905 -0.016930 nrc001   0.033455* nrc001     -436.03493002 RSIRFO TSBFGS     1    
  4   -436.03409164  0.00030673 0.029479 -0.016291 nrc001   0.036628* nrc003     -436.03477802 RSIRFO TSBFGS     1    
  5   -436.03397666  0.00011497 0.024398 -0.014618 nrc001   0.025590* nrc003     -436.03439177 RSIRFO TSBFGS     1    
  6   -436.03401006 -0.00003340 0.020774 -0.013117 nrc001   0.047532* nrc003     -436.03471917 RSIRFO TSBFGS     1    
  7   -436.03388070  0.00012936 0.015436 -0.010035 nrc001   0.044232* nrc003     -436.03441265 RSIRFO TSBFGS     1    
  8   -436.03385252  0.00002818 0.011054 -0.006465 nrc001   0.023115* nrc002     -436.03410472 RSIRFO TSBFGS     1    
  9   -436.03395665 -0.00010412 0.008142 -0.003933 nrc001   0.035079* nrc009     -436.03418642 RSIRFO TSBFGS     1    
 10   -436.03419321 -0.00023656 0.005794 -0.001160 nrc007  -0.034243* nrc001     -436.03425564 RSIRFO TSBFGS     1    
 11   -436.03429135 -0.00009814 0.004183 -0.000879 nrc008  -0.038455* nrc007     -436.03437881 RSIRFO TSBFGS     1    
 12   -436.03439849 -0.00010714 0.004730 -0.001132 nrc031  -0.036582  nrc001     -436.03444026 RSIRFO TSBFGS     1    
 13   -436.03442631 -0.00002782 0.004117 -0.000608 nrc007  -0.030021  nrc003     -436.03445488 RSIRFO TSBFGS     1    
 14   -436.03446108 -0.00003477 0.003591 -0.000733 nrc031  -0.082208* nrc002     -436.03451322 RSIRFO TSBFGS     1    
 15   -436.03452594 -0.00006485 0.001908 -0.000395 nrc025  -0.040603* nrc002     -436.03454248 RSIRFO TSBFGS     1    
 16   -436.03454486 -0.00001892 0.001135 -0.000261 nrc024  -0.076665  nrc003     -436.03456058 RSIRFO TSBFGS     1    
 17   -436.03456469 -0.00001983 0.001191 -0.000239 nrc021  -0.013547  nrc003     -436.03456701 RSIRFO TSBFGS     1    
 18   -436.03457548 -0.00001079 0.001127 -0.000219 nrc028  -0.018130  nrc003     -436.03457880 RSIRFO TSBFGS     1    
 19   -436.03457723 -0.00000175 0.000862 -0.000224 nrc021  -0.003912  nrc003     -436.03457810 RSIRFO TSBFGS     1    
 20   -436.03457652  0.00000071 0.000675 -0.000194 nrc021  -0.015747  nrc004     -436.03457818 RSIRFO TSBFGS     1    
 21   -436.03458079 -0.00000427 0.000616 -0.000129 nrc021  -0.004155  nrc004     -436.03458123 RSIRFO TSBFGS     1    
 22   -436.03458496 -0.00000418 0.000541  0.000110 nrc011  -0.009145  nrc056     -436.03458560 RSIRFO TSBFGS     1    
 23   -436.03458290  0.00000207 0.000478  0.000103 nrc007  -0.006157  nrc004     -436.03458317 RSIRFO TSBFGS     1    
 24   -436.03458145  0.00000145 0.000466  0.000090 nrc033  -0.002959  nrc056     -436.03458165 RSIRFO TSBFGS     1    
 25   -436.03458537 -0.00000392 0.000449  0.000084 nrc031  -0.003903  nrc056     -436.03458567 RSIRFO TSBFGS     1    
 26   -436.03459008 -0.00000471 0.000426  0.000099 nrc031  -0.015320  nrc056     -436.03459070 RSIRFO TSBFGS     1    
 27   -436.03458770  0.00000237 0.000491  0.000127 nrc057   0.004369  nrc056     -436.03458806 RSIRFO TSBFGS     1    
 28   -436.03457987  0.00000783 0.000387  0.000103 nrc057   0.003303  nrc056     -436.03458010 RSIRFO TSBFGS     1    
 29   -436.03457962  0.00000025 0.000313  0.000070 nrc057   0.011287  nrc056     -436.03457997 RSIRFO TSBFGS     1    
 30   -436.03458653 -0.00000691 0.000351  0.000069 nrc011  -0.006523  nrc056     -436.03458685 RSIRFO TSBFGS     1    
 31   -436.03458427  0.00000226 0.000312  0.000071 nrc028  -0.003912  nrc056     -436.03458441 RSIRFO TSBFGS     1    
 32   -436.03458566 -0.00000139 0.000297  0.000072 nrc031  -0.012541  nrc056     -436.03458608 RSIRFO TSBFGS     1    
 33   -436.03458660 -0.00000093 0.000269  0.000092 nrc001   0.007021  nrc056     -436.03458709 RSIRFO TSBFGS     1    
 34   -436.03458950 -0.00000290 0.000391  0.000085 nrc031  -0.003362  nrc056     -436.03458982 RSIRFO TSBFGS     1    
 35   -436.03458223  0.00000727 0.000204  0.000053 nrc028   0.001759  nrc056     -436.03458232 RSIRFO TSBFGS     1    
 36   -436.03458955 -0.00000732 0.000166  0.000051 nrc028  -0.001642  nrc010     -436.03458964 RSIRFO TSBFGS     1    
 37   -436.03458563  0.00000392 0.000223 -0.000056 nrc021  -0.001876  nrc001     -436.03458576 RSIRFO TSBFGS     1    
 38   -436.03459125 -0.00000562 0.000190  0.000042 nrc028   0.001066  nrc011     -436.03459131 RSIRFO TSBFGS     1    
 39   -436.03458578  0.00000547 0.000199  0.000071 nrc004   0.000906  nrc001     -436.03458584 RSIRFO TSBFGS     1(2) 
 
       +----------------------------------+----------------------------------+
       +    Cartesian Displacements       +    Gradient in internals         +
       +  Value      Threshold Converged? +  Value      Threshold Converged? +
 +-----+----------------------------------+----------------------------------+
 + RMS + 3.7825E-04  1.2000E-03     Yes   + 2.7080E-05  3.0000E-04     Yes   +
 +-----+----------------------------------+----------------------------------+
 + Max + 7.6874E-04  1.8000E-03     Yes   + 7.0770E-05  4.5000E-04     Yes   +
 +-----+----------------------------------+----------------------------------+
 
 Geometry is converged in  39 iterations to a Transition State Structure

matthew-hennefarth · 2024-12-20 17:11:42

As far as I know, analytical CASPT2 Hessians do not exists and the Hessians used during optimization/with &MCKINLEY are either semi-numerical or approximate. After you optimization, you should perform the Hessian calculation using &MCKINLEY.

Also, from my own experience, the default CASSCF convergence thresholds can often times not be tight enough for accurate semi-numerical Hessian calculations. I would suggest you add

THRS = 1.0e-10, 1.0e-06, 1.0e-06

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#1 2024-11-22 14:07:25

transition state OPT job converged but has 2 imaginary frequencies

#2 2024-12-20 17:11:42

Re: transition state OPT job converged but has 2 imaginary frequencies

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