Multiwfn forum

Dear Tian,

thank you again for the answer.

However, when I tried to derive the formula myself, I ended up with a similar, but slightly different expression. Namely, the MO expansion coefficients (C_mu,i) are grouped together corresponding either to two occupied or two virtual MOs:

C_mu,a*C_nu,b for i==j, a!=b
-C_mu,i*C_nu,j for i!=j, a==b

It seems also logical for me, because if we calculate the integral between two (CIS) excited state wavefunctions (similar like in Section 3.21.1.1 Theory 4), it will fall apart into integrals between singly excited configurations, and then only the terms with either the same MOs or different by only one MO will not be zero. In the singly excited configurations this means that either they have same occupied MO and different virtuals or different occupied and same virtual. In both cases the integral will reduce to the product of either two occupied or two virtual MOs.

And some more questions about the configuration coefficients: in the case of TDDFT calculation do I understand right, that the final expansion coefficient you use to calculate TDM is just the sum of the excitation and de-excitation coefficients for the corresponding pair of orbitals? At least it follows from the expansion on page 178 of the 3.6(dev) manual. Do you normalize or orthogonalize this coefficients somehow? Of the main interest for me are the coefficients provided by Gaussian09.

Thank you in advance,

Best regards,

Polina

First of all, thanks for the great work!
I have two questions regarding the transition dipole moments from the excited states: how do you calculate them? Do you integrate the corresponding transition dipole density?
And is it possible to obtain a cube file for a transition density between any excited states using Multiwfn?
Thanks in advance,
Polina