# [Pw_forum] one-electron contribution to the total energy

Paolo Giannozzi p.giannozzi at gmail.com
Wed May 25 09:44:36 CEST 2016

The "one-electron contribution" is the kinetic + pseudopotential energy.
Explanations hidden in this comment at line 524 of electrons.90:

! ... eband  = \sum_v \epsilon_v    is calculated by sum_band
! ... deband = - \sum_v <\psi_v | V_h + V_xc |\psi_v>
! ... eband + deband = \sum_v <\psi_v | T + Vion |\psi_v>

Paolo

On Tue, May 24, 2016 at 11:39 PM, Dumett Torres, Daniel <
dumettt2 at illinois.edu> wrote:

> Hello,
>
> I want to ask how the one-electron contribution is calculated in the
> report of the total energy after an scf calculation. I think my question
> amounts to asking: "what are the energies that are being used for the
> one-electron orbitals which when summed over with the correct occupancy
> give the one-electron contribution". My question was motivated by noticing
> that the band energies are given in eV and that summing over their values
> couldn't possibly give the sum total of the one-electron contribution that
> is given in Ry. (I checked this by integrating over the total density of
> states). It seems likely to me that the orbital energies are being
> referenced differently and that this is what causes the mismatch.
>
> I appreciate your help and explanation of my question
>
> Thank you for your help,
>
> Daniel Dumett Torres
> Graduate Student at the University of Illinois at Urbana-Champaign
>
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--
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
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