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Alex Granovsky
gran@classic.chem.msu.su

          $MASS group     (relevant for RUNTYP=HESSIAN, IRC, or DRC)

              This group permits isotopic substitution during the
          computation of mass weighted Cartesian coordinates.  Of
          course, the masses affect the frequencies and normal modes
          of vibration.

          AMASS = An array giving the atomic masses, in amu. The
                  default is to use the mass of the most abundant
                  isotope.  Masses through element 104 are stored.

          example - $MASS AMASS(3)=2.0140 $END
          will make the third atom in the molecule a deuterium.

Hope this helps.

Kind regards,
Alex

On Tue Dec 25 '12 5:30am, Panwang Zhou wrote
--------------------------------------------
>Dear Sanya and Alex,

>Thanks for your suggestions. Firsty I'll try to tighten the MCSCF convergence criteria.
>I'm not sure how to set to unity for all atomic masses in Firefly, could you please tell me how? Dear Prof. Alex. Thanks.

>On Mon Dec 24 '12 10:39pm, Alex Granovsky wrote
>-----------------------------------------------
>>Dear Panwang,

>>regardless on whether this particular imaginary frequency
>>is artifact or not, the better way to go away is to compute
>>normal modes for all atomic masses set to unity, then go away
>>along the computed imaginary mode as you described. You may need
>>to use larger multipliers though. The reason why one needs to set
>>masses to unity is that this will search for imaginary mode of
>>PES itself, rather than for imaginary mode of atomic vibrations.

>>Kind regards,
>>Alex Granovsky
>>
>>
>>
>>On Mon Dec 24 '12 5:55am, Panwang Zhou wrote
>>--------------------------------------------
>>>Dear all,

>>>Recently I carried out a geometry optimization using MCSCF(16,14) and then performed frequency calculation on the optimized geometry. The result indicated that there is one imaginary frequency (39.56I), then I generate the new coordinates with the following method:

>>>"Optimized Coordinates" + 0.5*"Imaginary Frequency" (Usually this is useful in Gaussian)

>>>and then re-optimized the geometry and perform frequency calculation, however, the imaginary frequency still existed (39.66I). I repeat the process again and I still get an imaginary frequency (40.27 I).

>>>It seems that the aboved method could not remove the imaginary frequency in Firefly. So, what's the correct way to remove imaginary frequency in Firfly? How to ajust the optimized geometry? Thanks.

>>>My input file：
>>>!   File created by MacMolPlt 7.4.3
>>> $CONTRL SCFTYP=MCSCF RUNTYP=OPTIMIZE EXETYP=RUN MAXIT=50 ICHARG=-1
>>>    MULT=1 FSTINT=.T. GENCON=.T. D5=.T. INTTYP=HONDO NOSYM=1
>>>    ICUT=11 ITOL=30 $END
>>> $SYSTEM MWORDS=300 TIMLIM=60000.0 KDIAG=0 NOJAC=100 $END
>>> $SCF DIRSCF=.T. FDIFF=.F. NCONV=8 $END
>>> $P2P P2P=.T. DLB=.T. $END
>>> $TRANS MPTRAN=2 DIRTRF=.T. AOINTS=DIST ALTPAR=.T. MODE=112 $END
>>> $MCSCF CISTEP=ALDET FULLNR=.F. SOSCF=.T. $END
>>> $DET NCORE=49 NACT=14 NELS=16 $END
>>> $BASIS EXTFIL=.T. GBASIS=TZVP $END
>>> $GUESS GUESS=MOREAD NORB=642 $END
>>> $STATPT NSTEP=200 METHOD=GDIIS OPTTOL=0.00001 HSSEND=.T. $END
>>> $FORCE NVIB=2  $END
>>> $DATA
>>>Title
>>>C1
>>>C    6.0        2.7132783145    -1.4740302589   -.0597953357
>>>C    6.0        4.0072333395    -1.0587405339   -.0523177056
>>>C    6.0        4.3509360614    .3549750338     .0047198534
>>>C    6.0        3.2110719721    1.2609116970    .0544028295
>>>C    6.0        1.9242681910    .8199231769     .0449917837
>>>C    6.0        1.5962366929    -.5763413550    -.0135105729
>>>H    1.0        2.5090291816    -2.5321904000   -.1049181082
>>>H    1.0        4.8194252269    -1.7639108567   -.0902441560
>>>H    1.0        3.4295424902    2.3141043298    .1003293599
>>>H    1.0        1.1243498618    1.5313547817    .0836053890
>>>C    6.0        .3110181302     -1.1305273538   -.0277143026
>>>H    1.0        .3099287926     -2.2086654130   -.0629691982
>>>C    6.0        -.9868693392    -.6482779462    -.0084178737
>>>C    6.0        -1.5542949968   .6857027999     .0186426827
>>>C    6.0        -3.1400841402   -.9091688721    -.0109188077
>>>N    7.0        -2.0507028080   -1.5755767961   -.0262051103
>>>N    7.0        -2.9262976042   .4589864153     .0171317950
>>>O    8.0        -1.0737305753   1.7997169650    .0373172595
>>>C    6.0        -3.9107928678   1.4991176546    .0280233794
>>>H    1.0        -3.3895141243   2.4438580486    .0569467246
>>>H    1.0        -4.5338570060   1.4747095620    -.8621195135
>>>H    1.0        -4.5568760150   1.4328337955    .8991551602
>>>C    6.0        -4.5112041528   -1.4987819631   -.0176023140
>>>H    1.0        -4.4221489875   -2.5756182595   -.0409245327
>>>H    1.0        -5.0740697743   -1.2147434323   .8678104944
>>>H    1.0        -5.0821323510   -1.1773397307   -.8848586971
>>>O    8.0        5.5107321775    .7514431412     .0110739666
>>> $END
>>>--- OPTIMIZED MCSCF MO-S --- GENERATED AT  0:43:41 19-DEC-2012
>>>Title
>>>E(MCSCF)=     -719.8906562926,  0 ITERS, E(NUC)=  996.3878966217
>>> $VEC
>>> 1  1-1.36077782E-06 6.69461457E-06-1.32096704E-04 7.44449420E-04 9.20147697E-04
>>>....
>>> $END