[Pw_forum] A little question about total energy
Paolo Giannozzi
giannozz at nest.sns.it
Fri May 16 15:28:49 CEST 2003
Hi
> In the output of PWSCF, the energy partitions are list
> following the total energy as I pasted below. I found
> that the total energy is not equal to the sum of those listed
> partitions.
Total Energy = sum of terms marked with "+" below =
one-electron + hartree + xc + ewald + correction for metals
! total energy = -62.07569469 ryd
estimated scf accuracy < 0.00000799 ryd
band energy sum = -14.82580512 ryd
+ one-electron contribution = -98.79712762 ryd
+ hartree contribution = 51.10053218 ryd
+ xc contribution = -14.02297161 ryd
+ ewald contribution = -0.34484385 ryd
scf in/out correction = 0.02901784 ryd
+ correction for metals = -0.01128379 ryd
The "one-electron contribution" is the kinetic + ionic term:
\sum <psi| T + V_ion | psi>
The "band energy sum" is exactly what it claims to be:
\sum epsilon = \sum <psi| T + V_ion + V_scf | psi>
The "correction for metals" makes forces and energies
consistent if a broadening scheme is used.
The "scf in/out correction" is no longer used
(and no longer useful)
The "estimated scf accuracy" gives an estimate of the
error on the energy due to imperfect self-consistency.
Admittedly, it is slightly confusing.
Paolo
--
Paolo Giannozzi e-mail: giannozz at nest.sns.it
Scuola Normale Superiore Phone: +39/050509412
Piazza dei Cavalieri 7 Fax: +39/050509417, 050563513
I-56126 Pisa, Italy Office: Lab. NEST, Via della Faggiola 19
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