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

[Giuseppe Mattioli]

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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