[Pw_forum] visualization of the orbitals produced with the hybrid functional

[Layla Martin-Samos]

Dear Alexey, even in the case of Hartree-fock and occupied states is
difficult to notice with the eyes a big difference. Indeed, nature is
mainly mean-field and the biggest differences between standard DFT and
hybrid DFT schemes are in the tail of the wave functions.

cheers

Layla

2012/11/7 Giuseppe Mattioli <giuseppe.mattioli at ism.cnr.it>

>
> Dear Alexey
>
> I've plotted many HOMO and LUMO orbitals of small and large molecules by
> using the HSE or the B3LYP
> functional. They are often very similar to their PBE or BLYP counterparts.
> This is not accountable
> for an incorrect behaviour of the pp.x code. It is only the fact that,
> apart from some particular
> cases like those involving atomic-like d orbitals of transition metals
> contained in a C-N-O-H
> molecular environment, the pure DFT density is not so different from the
> hybrid density. After all,
> when you perform a B3LYP calculation you are only substituting about 20%
> of BLYP exchange with
> Hartree-Fock exact exchange... Not a great difference ;-)
>
> HTH
>
> Giuseppe
>
> On Tuesday 06 November 2012 18:54:00 Alexey Akimov wrote:
> > Dear all,
> >
> > I calculated the charge density for some KS orbitals(lets say HOMO and
> > LUMO) - using the pp.x program and the converged scf reslts for PBE and
> > PBE0 functionals. The orbital energies obtained with the PBE0 give much
> > better estimate for the band gap than those obtained with the PBE, what
> is
> > expected. However I also expected to see some (substantial or at least
> > minor) difference of the orbitals (the spatial localization of the
> > corresponding charge densities), produced by PBE vs. PBE0 functionals.
> Yet
> > when visualizing they look quite the same. So is this a problem of the
> > pp.x (which probably only accounts for the part of the density produced
> > with the "pure" part of the PBE0 functional), is this something more
> > fundamental what leads to similar orbital-projected charge densities of
> > the pure and hybrid functionals or is this something I missing in the
> > input files? I copy my input for pp.x below.
> >
> >  &inputpp
> >     prefix  = 'x'
> >     outdir = './'
> >     filplot = 'tmp.dat'
> >     plot_num= 7
> >     kpoint=1
> >     kband=222
> >  /
> >
> >  &plot
> >     nfile = 1
> >     filepp(1) = 'tmp.dat'
> >     weight(1) = 1.0
> >     iflag = 3
> >     output_format = 6
> >     fileout = 'x-KS_222.cube'
> >  /
> >
> >
> >
> > Thank you,
> > Alexey
>
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>    Giuseppe Mattioli
>    CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
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