What is the difference between DC coupling with ETF , cis force matrix element and cis derivative coupling without etf

[harsh]

While calculating nac between S0 and S1 states, I have these three ouputs. Which one should i be considering to describe my nac vector and calculate coupling. does etf means energy scaled by the difference.

[kaushik]

Please refer to some of the related references; e.g., https://pubs.aip.org/aip/jcp/article/141/2/024114/352388/Derivative-couplings-between-TDDFT-excited-states#74644882

[jherbert]

See also the response here:

How to interpret non adiabati coupling output

These are the derivative coupling vectors d^(x), as defined for example here: Multiplying by the energy gap gives you what is normally called the nonadiabatic coupling h^(x).