Definition of non-adiabatic coupling in MOLPRO

[Shaowei Nie]

Dear all,

I am kind of the confused by the actual definition of non-adiabatic coupling (NAC) taken by MOLPRO since I can't find the reference paper that the codes may adapt. Is it equivalent to the derivativte coupling ,i.e., <a|d/dQ|b> (a and b are wave functions) or <a|dH/dQ|b>? For the latter one, a further division by the adiabatic energy is needed to get the derivative coupling.

Any information is appreciated!

Shaowei Nie