[Octopus-users] Difference between TDLDA and TDDFT

[Juzar Thingna]

Hello,
I have been calculating the photo-absorption of simple clusters using Casida
and TDDFT using LDA in Octopus. As bench marks I have used Si2H6 and SiH4
clusters.
I tried comparing my results to another calculation on the same clusters
using TDLDA under the linear response theory. The results of Octopus are
more closer to the experimental data but differ from the TDLDA method.
Please could you explain why the Octopus results should differ from TDLDA?
Any references to clarify my doubt would be of great help.

          Transition    TDDFT    TDLDA    Experiment
SiH4       4s               8.7          8.2             8.8
               4p               9.4          9.2             9.7
               4d              10.7         9.7           10.7
Si2H6     4s                7.3          7.3            7.6
               4p                8.3          7.8            8.4


Regards,
Juzar

-- 
"At the end of all our searching we will arrive at the place we began and
know it for the first time."
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