[Pw_forum] Excited State Gradients in TDDFT

[Stefano Baroni]

On Feb 2, 2012, at 7:47 AM, yukihiro_okuno at fujifilm.co.jp wrote:

> Dear PWSCF users and developers.
> 
> I want to know the possibility of excited state gradients in TDDFT implemented in 
> 
> Quantum Espresso.
> 
> Can the PWSCF calculate the excited state gradients (Force of atoms in excited state )
> 

pwscf does not implement any excited-state features (tddft energies, gradient or other). The QE distribution does contain some specialized codes that perform some of these calculations (turbo_tddft implements the Liouville-Lanczos approach to TDDFT, whereas GWL is an implementation of the GW method particularly suitable for large systems)
> 
> by PWSCF, or are there plan to develop the excited state gradient calculation ? 
> 
> The implementation of TDDFT in PWSCf uses lanczos method and does not 
> 
> explicitly calculate the excited energy, and is it difficult to extend to 
> 
> calculate force in this formalism ? 
> 

the present implementation of tddft is particularly suited for the calculation of the entire spectrum of large systems, whereas excited-state energy gradients would require the calculation of individual eigenpairs of the Liouvillian. That should not be difficult to implement, but it is not considered to be a priority at this time. Should anybody be interested in implementing this feature, we in Trieste would be delighted to help.

SB

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Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center - Trieste
http://stefano.baroni.me [+39] 040 3787 406 (tel) -528 (fax) / stefanobaroni (skype)

La morale est une logique de l'action comme la logique est une morale de la pensée - Jean Piaget

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