TDDFT+U with Casida vs. time-propagation

[ashwin_r]

Hello,

In the context of DFT+U/TDDFT+U, a previous thread noted that the Hubbard U is included only in the ground-state calculations but not in the response function calculation, i.e., it is missing in fxc. This information was from 2021 when only the Casida approach was available to perform TDDFT (as far as I recall).

Seeing that time-propagation (TIMEEV) is available, I would like to clarify whether the Hubbard U can now be included in the TDDFT step, i.e., when updating the Hamiltonian at each time step.

Thanks!

[henrique_miranda]

Hi,
Yes in principle Hubbard U can be included with TIMEEV.
As a sanity check you can compare the results for the real part of the static dielectric tensor obtained from TIMEEV with the ones obtained with LCALCEPS=.TRUE.
Since U is supported with LCALCEPS the results should match the ones of TIMEEV.

[ashwin_r]

Thanks, Henrique.

BTW, there is a bug in the subroutine XML_EPSILON_E_DIR (file xml.F) that affect the output of the dielectric function for IEPSILON>1. I have documented the fix in the bug-reports forum.