[DFTB-Plus-User] Help required: DFTB+ linear response calculation: Request for X and Y Coefficients for Individual Transitions in Excited States

[Anant Bhasin]

Dear DFTB-plus users,

Greetings! I am new to DFTB+.

I had a query about Linear response calculation which I ran for Ag2. The
following is the input file.

""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
Geometry = xyzFormat {
    <<< "Ag2.xyz"
}

Driver = {}

Hamiltonian = DFTB {

    SCC = yes
    SCCTolerance = 1.0E-10
    MaxAngularMomentum = {
        Ag = "d"
    }
    SlaterKosterFiles = Type2FileNames {
        Prefix = "../../slako/hyb/hyb-0-2/hyb/hyb-0-2/"
        Separator = "-"
        Suffix = ".skf"
    }
# Only include this if I want to see triplet states
#    SpinConstants = {
#        N = {-0.026} # HOMO Wpp
#    }
}

ExcitedState {
    Casida {
        NrOfExcitations = 70
        Symmetry = singlet
        Diagonaliser = Arpack{}
        WriteSPTransitions = yes
        WriteTransitions = yes
        WriteTransitionDipole = yes
        WriteCoefficients = yes
        StateOfInterest = 1
        WriteEigenvectors = yes
#        WriteTransitionDipole = yes
        WriteXplusY = yes
    }
}
""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""

I am able to generate the XplusY.DAT file (which I understand contains the
excitation and deexcitation coefficients—please correct me if this is
incorrect). However, I would like to obtain the individual X and Y
coefficients for each transition that contributes to a specific excited
state. In the transition output file, I can see all the transitions
contributing to an excited state, but only the weights are provided, not
the X and Y coefficients.

Any help will be appreciated.

Best,
Anant
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