# FSSH Hopping probability between states

Hi all

I was playing around with FSSH on ethylene and set the number of allowed surfaces to be 20 (singlets). At the end of each time step there is a “Hopping probability” value, which is self explanatory. What I am wondering is: Is that value the total probability to hop to any allowed state?

Is there any way I can look at the hopping probability to each individual allowed state? In my case its 19 states excluding current state so there should be 19 P_ij values, where i is current state and j is some other state

Thanks in advance for any help

Can you please post a snippet from the output, or maybe a simple input file?

Attached figure is a screenshot of the .out file with Hopping probability.

Below is the input .inp file:

\$molecule
0 1
C 1.85082356 -1.78953123 0.00000000
H 2.38603593 -2.71605577 0.00000000
H 0.78082359 -1.78977646 0.00000000
C 2.52815456 -0.61573833 0.00000000
H 1.99294220 0.31078621 0.00000000
H 3.59815453 -0.61549310 0.00000000
\$end

\$rem
JOBTYPE freq
METHOD hf
basis 6-31g*
\$end

@@@

\$molecule
\$end

\$rem
jobtype aimd
exchange hf
basis 6-31g*
cis_n_roots 2
symmetry off
sym_ignore true
cis_singlets true
cis_triplets false
proj_transrot true
fssh_lowestsurface 0
fssh_nsurfaces 2
fssh_initialsurface 1
afssh 0
cis_der_couple true
aimd_steps 600
time_step 10
aimd_short_time_step 2
aimd_time_step_conversion 1
aimd_print 1
aimd_init_veloc zpe
aimd_integration vverlet
\$end

There is only 2 surfaces in this case but the issue is still presented. I wish to see the hopping probability from current state to all allowed state.
Thanks again for any help!

Someone who knows this code better can correct me, but after poking around in the code a bit, it does not appear as if this has been implemented in a way that is user-accessible from the input file. You could make a feature request, as it feels like it should be a relatively minor change to the AFSSH code

Thanks for hopping in this, John. You are correct that there is not currently a user-facing method for printing all hopping probabilities. And, as you suggest, it wouldn’t be too difficult to implement.