Reaction Path following by QSD

Jorge Luis LLanio Trujillo jolla at
Tue May 23 09:59:34 BST 2000

Dear people:

I decided to poster to the molpro mailing
list ONLY after many hours of efforts. I really need some help to solve
this problem(or at least some tips)

I want to generate the reaction path from TS to products and that from TS
to reactants(i.e. i want to reach reactant and product minima) and also i
want to obtain the geometries, energies and projected vibrational
frequencies at the points calculated along the path(if possible, well
suited for the prospect of VTST) . 

Level of theory : CASSCF(8,8)/6-311G(2d,f)
I have 3 distances r1,r2,r3 ; 2 bonding angles c1,c2 & one dihedral angle

My molpro input file looks like:

{Z-matrix input; basis set input; transition state(TS) starting geometry 
           ; wave function definition(spin & spatial symmetry as well as
             the orbital space partitioning) , NOT INCLUDED as it seems to
             me not important in the context of my question}


I start the integration of the MEP at the transition state geometry(I am
sure that this is a real TS at CASSCF(8,8)/6-311G(2d,f) because in a
previous molpro run, starting at some initial guess, i reached it and
after being calculated the frequencies i got only one imaginary) and the
first step is taken along the "transition vector"(IDIR=1, see above)

To my surprise, i got only one point , which is indeed the starting 
point(namely, the TS from which I began) and the integration terminate. It
seems to me that the integration should terminate at product(reactant)
minima structures. Any Tips?
What follows is a partial output of the optimization history:

 ENERGIES -299.246708

           R1            1.2529757
           R2            1.3785954
           C1          111.3507527
           R3            1.9953596
           C2          104.0520245
           FI           86.2868481

           R1           -0.0000001
           R2            0.0000000
           C1            0.0000000
           R3            0.0000001
           C2            0.0000000
           FI            0.0000000

                             IDIR  =        -1

 Quadratic Steepest Descent -  Reaction Path Following using updated

 In QSD: Reaction Path coordinates, scaled to the original units:

 Optimization point 1



         Jorge Luis LLanio(jolla at
         PhD. student
         University of Coimbra

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