[CPMD-list] Transition Dipole Moment in PROP and TDDFT

[Hua Bao]

Dear CPMD-user,

In section PROP of CPMD, there is a keyword "Transition Moment". It is 
the transition matrix element between to orbitals. Also, when you are 
doing an electronic spectra calculation with TDDFT. There will be a 
transition dipole moment output.

Based on my understanding, the first transition dipole moment is just 
the integral of two different ground state KS orbitals. The transition 
dipole moment in TDDFT describes the transition between the n-th excited 
state and the ground statss. Am I right? If it is the case, what is the 
physical meaning of the first transition dipole moment? Can it be used 
to determine absorption spectra and transition rate, etc?

If I calculate the first transition dipole moment for periodic solid, 
then what is the physical meaning?

Thanks,
Hua