Molcas Forum

csalguero

Member

Registered: 2024-07-05

Posts: 1

NAC usage in nonadiabatic molecular dynamics calculations

I hope all is well! We had some questions regarding the nonadiabatic coupling vectors and their use during nonadiabatic molecular dynamics in MOLCAS.  We know that MOLCAS uses the CI overlap to approximate the NAC. This value is then used in Tully's FSSH to determine whether a hopping event occurs (e.g. when we call the &ALASKA module without any keywords). If we call the NAC keyword explicitly within the &ALASKA module (e.g., NAC = 1 2), will the calculated NAC value be used instead of the CI overlap? If it uses this value, how does it affect the outcome of the dynamics?

Leo

Member

Registered: 2018-11-20

Posts: 15

Re: NAC usage in nonadiabatic molecular dynamics calculations

I may be wrong (I am just a user), but I don't think that's possible. The possibility is either to use RASSI to calculate overlaps or to use CI vectors products, but as far as I know if you want to exploit the analytically computed NACs you probably have to rely on external interfaces.

The second question is a bit wide, but here is a possibly interesting reference:

https://doi.org/10.1021/acs.jctc.2c00968