[Pw_forum] electronic excitation energy

[Stefano Baroni]

Those concepts refer to finite-temperature calculations. Only zero-temperature DFT is implemented in QE (as well as in many other similar packages). For reasonably low temperatures (up to the typical melting temperature of typical materials and above, but still well below the Fermi temperature) this is deemed to be a very good approximation. In this regime, thermal effects only affect the nuclear motion, which can be dealt with in the QHA or using AIMD. Still, QE uses the concept of "electronic temperature" (or smearing) to deal with with Fermi-surface effects and Brillouin-zone sampling, but this should be regarded more as a numerical device, than as a way to deal with thermal excitations of the electronic degrees of freedom. As always, a proper signature of the posts, including an affiliation, is considered a sign of politeness and is therefore highly appreciated in this forum. SB

On Jun 21, 2012, at 5:54 AM, bhabya sahoo wrote:

> F(V, T) ) Estatic(V) + Fphon(V, T) + Felec(V, T)
> where Estatic(V) is the energy of a static lattice at zero temper-
> ature; Felec(V,T) is the thermal free energy arising from electronic
> excitations; and Fphon(V,T) is the phonon contribution. Both
> Estatic(V) and Felec(V,T) can be obtained from first-principles
> calculations directly. Density functional perturbation theory
> (DFPT) is a well-established method for calculating the
> vibrational properties from first-principles in the framework of
> QHA
> 
> 
> 
> 
> On Thu, Jun 21, 2012 at 7:29 AM, Arles V. Gil Rebaza <arvifis at gmail.com> wrote:
> Dear Bhabya, please read this paper.
> 
> Computer Physics Communications
> Volume 182, Issue 10, October 2011, Pages 2232–2248
> http://www.sciencedirect.com/science/article/pii/S0010465511001652
> 
> Stefano, in this paper are about the "static energy"
> 
> Best
> 
> PhD std Arles V. Gil Rebaza
> IFLP - Argentina
> 
> 
> 2012/6/20 Stefano Baroni <baroni at sissa.it>
> Would please define (with a formula or a reference to a published book/paper) the three terms, particularly the first two? ("static" and "electronic") - SB
> 
> --
> Stefano Baroni, Trieste -- swift message written and sent on the go
> 
> On 20/giu/2012, at 20:18, bhabya sahoo <bdslipun at gmail.com> wrote:
> 
> > As we know that the total energy is the sum of static energy, electronic energy, and vibrational energy the first energy is the out put of scf file in quantum espresso and the second one is the output of QHA  code but how the electronic energy is calculated from first principle
> >
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> > any suggetions  how it can be included in the total energy
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> > sahoo b
> > mumbai reserch scholar
> >
> > _______________________________________________
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> 
> -- 
> ###--------->   Arles V.   <---------###
> 
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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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