# Programs for Real Wavepacket Propagation

## Exact Calculations using Real Wavepacket propagation

This is an exact calculations using real wavepacket. One can do
this calculations using MCTDH input/operator file (for
*exact* calculations) with little modifications. In the run
section *'realwp'* keyword need to use, which will generate
initial real wavepacket from MCTDH *exact* complex
wavepacket. Other things in the run section will be like
*exact* calculations in MCTDH program. But right now it
calculate only reaction probability using flux operator. Use
*probrw* for calculating probability. For more details about
real wavepacket dynamics referred to S. K. Gray J. Chem. Phys.
**96**, 6543(1992), Gray et al. J. Chem. Phys.
**108**, 950(1998), Hankel et al J. Chem. Phys.
**125**, 164303(2006). Please email to Dr Anthony J.
H. M. Meijer (a.meijer@sheffield.ac.uk) for any problem in
using.

## Operator Section

Energy cut-off (V < R only) is essential here. Which will set
maximum to R for potential energy, total rotational terms (means
j_{1}^{2} +
j_{2}^{2}+...+j_{cent+K}^{2})
and Coriolis-coupling terms, separately. Similar way this will use
the minimum for Coriolis-coupling term(s), if you have any. We have
to do this to make sure the eigen values of Hamiltonian operator of
the system are in -1.0 to +1.0 range.

Since we are using real wavepacket for propagation we could not
use *CAP*, we use real function (Gray et al J. Chem. Phys.
**91**, 7671(1989), keyword *DAMP*, to damp the
wavefunction at the edge of the grid. Calculation of flux operator
is carried out analytically only for wrapped sinc DVR basis,
keyword *fluxws*. So, one need to use wrapped sinc DVR basis
for coordinate along which flux to be calculated.

## Integrator Section

One need to give maximum and minimum value of the Hamiltonian to
shift and scale the Hamiltonian(Tal-Ezer et al J. Chem. Phys.
**81**, 3967(1984), H --> f(H), keyword *hscale
= E_min, E_max*. From experience it is found that the difficult
job to define *E_min* and *E_max*. One need to
calculate wavefunction at t=1 from t=0 using Chebychev iteration to
start the integration, for that need to define number of Chebychev
iteration, keyword *ncheb=N*. To calculate the flux we have
to provide a number (*fluxsave*) (every *fluxsave*
time steps it will be calculating flux), energy window
(*femin,femax*) and number of energy points (*prne*)
for calculating Probability. *Fluxsave* number will be
modified by the energy window used for calculating the probability.
Keyword for this *eprob = fluxsave, prne, femin, femax*