The time-dependent current-density-functional (TDCDFT) implementation is built entirely upon the normal TDDFT implementation. Therefore all general remarks that are made for the TDDFT part of the program are also valid for TDCDFT. Only the polarizability and excitation energies of closed shell molecules can be calculated with TDCDFT in the present implementation.
If TDCDFT is used together with the ALDA functional (NOVK option) it will give the same results for the polarizability and excitation energies as TDDFT in a complete basis set. TDCDFT in ADF by default uses the VK functional [160,161], since this is the only current dependent functional that is known presently. Many aspects of the functional are still unknown and the functional should therefore be used with caution. The user is referred to the references for more information on when the VK functional gives good results and when not.
For more information on the implementation and applications of the TDCDFT and the VK functional please read the references: [162-165]. For more details on the theory and implementation in ADF see: [166].
To activate TDCDFT and the VK functional one should add the following block key to the input file:
CURRENTRESPONSE
END
To calculate the polarizability the keyword Response can be used with the following options:
RESPONSE
ALLCOMPONENTS
Nfreq Nfreq
FrqBeg FirstFreq
FrqEnd LastFreq
[Optional Frequency/Energy Unit]
END
The block key EXCITATION can be used with all of its options.
In default the VK functional will be applied where the NCT parameterization [167] is chosen for the transverse exchange-correlation kernel for the polarizability and singlet excitation energies (giving the best results for the systems studied so far). For triplet excitation energies the only available parameterization will be used [168]. This option is not tested much and the results are in general much worse than ALDA [166]. It is therefore suggested that VK is not used to calculate triplet excitation energies.
In the output the polarizability tensor (in case of an ALLCOMPONENTS calculation) has a different shape, the results are printed in the more intuitive order x, y, z, instead of y, z, x that the TDDFT implementation uses.
The following subkeys are available within the datablock of CURRENTRESPONSE
CURRENTRESPONSE
QIANVIGNALE
NOVK
END
QIANVIGNALE
The QV parameterization [168] will be used for the transverse exchange-correlation kernel instead of NCT.
NOVK
TDCDFT will be applied with the ALDA functional instead of the VK functional. In a complete basis this will give the same results as a TDDFT calculation.
