***** Tutorial for Saddle Point and IRC calculation *****

In this tutorial, saddle point (transition state) of 
an internal rotation of a metyl group about the central C-C bond
is calculated. Thereafter IRC calculation is performed.

---------------------- Included files -------------------------

Et1.pdb    Initial guessed structure for saddle point calculation
Et1.inp    GAMESS input file for saddle point calculation
Et1.out    GAMESS output file
Et1.pun    GAMESS punch file

Et2.pdb    Saddle point structure
Et2.inp    GAMESS input file for IRC calculation
Et2.out    GAMESS output file
Et2.pun    GAMESS punch file
Et2.irc    GAMESS irc file which contains IRC data

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#################   Finding Saddle Point  ############################

(1) Guess an initial structure for saddle point

Make a reasonable guess at a saddle point structure 
using chemical intuition. 
Et1.pdb is a guessed structure.

(2) Calculate Hessian matrix for the guessed initial structure

Unlike geometry optimization,
it is essential that one starts a saddle point search
with a calculated Hessian matrix.

To calculate Hessian matrix, run GAMESS with RUNTYP=HESSIAN.

You should see the following message.

     This is NOT a stationary point of the molecular PES

Don't worry about that. It is normal since the initial structure
is not a stationary point. We are not interested in the vibrational
analysis now, because obtaining the resulting $HESS (Hessian matrix)
is the purpose of this calculation.

To retrieve the Hessian matrix into Facio,
select File menu > Get $HESS group from GAMESS Punch
and read GAMESS punch file (Et1.pun in this case).
Then you will see the following message.

     $HESS group was successfully retrieved.

(3) Optimization of saddle point

To do this, run GAMESS with RUNTYP=SADPOINT

$STATPT HESS=GUESS will be changed automatically
to HESS=READ. If Hessian matrix was not retrieved
a warning message will appear.

After the calculatio, Et1.inp, Et1.out, Et1.pun 
will be produced and you will see the following message.

     *** Saddle Point Located ***

Save this saddle point structure 
by File menu > Save As (HETATM/CONECT) format PDB file
This is Et2.pdb.

(4) Perform a vibrational analysis at the saddle point

To do this, run GAMESS with RUNTYP=HESSIAN

If you see the following message, it is confirmed that 
the saddle point is really a transition state.

     Number of Imaginary Frequency : 1
     There is Only ONE Imaginary Frequency at Normal Mode #1


If the number of imaginary frequency is 0 or more than 1,
the saddle point is not a transition state.

#######################  IRC calculation  ###########################

Since the structure and vibrational analysis at the transition state
do not always unambiguously identify the reactant and product,
a proof that a certain transition state does indeed connect a particular
reactant and product is necessary. 
IRC calculation provides such a proof.


(1) Get the Hessian matrix of the transition state

To retrieve the Hessian matrix into Facio,
select File menu > Get $HESS group from GAMESS Punch
and read GAMESS punch file (Et2.pun in this case).

(2) Perform IRC calculation

To do this, run GAMESS with RUNTYP=IRC

You should see the following message.

     Be sure to get the latest Hessian matrix ...

The latest Hessian matrix is the Hessian matrix of
the saddle point, <<not>> the one used for saddle point search.

After the calculation, Et2.irc is produced.

(3) Viewing the IRC data

Et2.irc contains IRC data.
To read the data, select File menu >> Load New GAMESS IRC Data
and load Et2.irc. 
If it is successfully loaded, Tools menu >> IRC Data is enabled.

Select Tools menu >> IRC Data and a new control panel will appear.
Change the IRC Point # slide in the control panel and 
the corresponding structure at the IRC point will be shown.
If the metyl group rotates, it is confirmed that the transition state
is really the one for the internal rotation of the metyl group.

Note that one half of the IRC is found at this point and
the other half should be calculated.

(Calculation results of the other half are
 not included in this tutorial.)

To calculate the other half of the IRC,
run GAMESS with RUNTYP=IRC and FORWRD=.TRUE.


    End of Tutorial for Saddle Point and IRC calculation
##################################################################
