Hi Ben,
I guess the point here is that the virial theorem asserts that one
must take the time average of the total mechanical energy, which will
be equal to the minus time average of the kinetic energy. As you
showed only the final values, I assume you're taking the values at a
particluar time. The virial theorem has no basis on this ground, since
even in classical mechanics the total mechanical energy E=T+V at any
time, but only the average values are taken on virial theorem.
Best regards,
Marcelo Zimmer
===================================================
Marcelo Zimmer S. Flores
(PhD Physics Student)
Address:
Universidade Estadual de Campinas - UNICAMP
Instituto de Fisica Gleb Wataghin - IFGW
Grupo de Solidos Organicos e Novos Materiais - GSONM
Departamento de Fisica Aplicada (DFA) - Room 61
Campinas - Sao Paulo - Brazil
13083-970
Caixa Postal: 6165
[email protected]
===================================================
Em 08/12/2009, às 00:21, Ben Martin <[email protected]> escreveu:
> I'm having trouble resolving the energy output in SIESTA,
> specifically that it seems to violate the virial theorem. The virial
> theorem requires that the EXACT solution must satisfy kinetic energy
> = - total energy, but I'm not getting anywhere close to that.
> Below is the energy output of an optimization I ran:
>
> Final energy (eV):
> Kinetic = 5497.928558
> Hartree = 2350.057707
> Ext. field = 0.000000
> Exch.-corr. = -1786.932583
> Ion-electron = -9917.735789
> Ion-ion = -3791.753153
> Ekinion = 0.000000
> Total = -7648.435261
>
> The relaxation runs fine and the relaxed coordinates are good, but
> as you can see there is a discrepency of ~2000 eV (or about 30%)
> between Kinetic and -Total.
>
> Am I missing something?
>
> Thanks,
> Ben
>
> *************************************
> #General system specifications
> SystemName Olivine
> SystemLabel Ol
> NumberOfAtoms 28
> NumberOfSpecies 3
>
> %block ChemicalSpeciesLabel
> 1 12 Mg # Species index, atomic number, species label
> 2 14 Si # Species index, atomic number, species label
> 3 8 O # Species index, atomic number, species label
> %endblock ChemicalSpeciesLabel
>
> AtomicCoordinatesFormat Ang
>
> %block LatticeVectors
> 4.6300 0.00000 0.00000
> 0.0000 9.96000 0.00000
> 0.0000 0.00000 5.98000
> %endblock LatticeVectors
>
> %block AtomicCoordinatesAndAtomicSpecies
> 28 atom coordinates, etc.
> %endblock AtomicCoordinatesAndAtomicSpecies
>
> %block GeometryConstraints
> position 1
> %endblock GeometryConstraints
>
> %block PAO.Basis
> bases from the SIESTA database
> %endblock PAO.Basis
>
> XC.Functional LDA
> XC.Authors CA
>
> MeshCutoff 300.0 Ry
> MaxSCFIterations 600
> DM.MixingWeight 0.01
> MD.TypeOfRun CG
> MD.NumCGSteps 600
> MD.VariableCell
>
> SolutionMethod diagon
> AtomCoorFormatOut Ang
>
> MD.MaxForceTol 0.004 ev/Ang
> DM.Tolerance 1.d-4
> DM.EnergyTolerance 1.d-4 ev
> MD.MaxCGDispl 0.000635 Ang
>
> WriteForces .true.
>
>
