TD-DFT energies

[Miguel RP]

Hi All,

I'm running a TD-DFT calculation on a flake system composed of C, Ti, and O atoms.

When using the PBE functional, the calculation finishes successfully, but the excitation energies seem suspiciously low:

         State    Excitation      
         number   energy (eV)    
         ----------------------------------------
 TDDFPT|      1       0.08219  
 TDDFPT|      2       0.11190  
 TDDFPT|      3       0.14461  
 TDDFPT|      4       0.15730   
 TDDFPT|      5       0.17494 
 TDDFPT|      6       0.18766   
 TDDFPT|      7       0.21300  
 TDDFPT|      8       0.22745
 TDDFPT|      9       0.24470
 TDDFPT|     10       0.26010  

I’ve attached my input file in case anyone is willing to take a look and help identify anything that might be causing this behavior.

I've also tried using the PBE0 hybrid functional, but the calculation gets stuck during the SCF procedure and doesn’t seem to make progress—even after running for over a day. It stays at the following output:

  
 SCF WAVEFUNCTION OPTIMIZATION

  Step     Update method      Time    Convergence         Total energy    Change
  ------------------------------------------------------------------------------

  HFX_MEM_INFO| Est. max. program size before HFX [MiB]:                     490

 *** WARNING in hfx_energy_potential.F:587 :: The Kohn Sham matrix is not  ***
 *** 100% occupied. This may result in incorrect Hartree-Fock results. Try ***
 *** to decrease EPS_PGF_ORB and EPS_FILTER_MATRIX in the QS section. For  ***
 *** more information see FAQ: https://www.cp2k.org/faq:hfx_eps_warning    ***

I’ve already tried decreasing EPS_PGF_ORB and EPS_FILTER_MATRIX as suggested, but the issue persists.

Thanks in advance!

Best,

Miguel

[Jürg Hutter]

Hi

you are mixing PBE/PBE0, at least in the input you posted. See basis sets/ pseudopotentals
and referenz functional for D3. However, this is not causing problems, it is just bad practice.

If you want to use PBE0 for this system and basis set, I would strongly encourage to use
ADMM. You can find many example inputs in the tests/QS section.

regards
JH

________________________________________
From: cp...@googlegroups.com <cp...@googlegroups.com> on behalf of Miguel RP <miguel...@gmail.com>
Sent: Wednesday, April 23, 2025 4:08 PM
To: cp2k
Subject: [CP2K:21411] TD-DFT energies

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