[Wien] Meta-GGA

[Stefaan Cottenier]

Peter Blaha is the one who can give you all the details, but as he is 
on holiday I give my opinion on your problem (no correctness 
guaranteed):

The (unknown) correct XC-functional should give you the correct total 
energy. All actual implementations of DFT use approximations (LDA, 
GGA) that give you only a crude approximation of the total energy 
(several Ry wrong). Fortunately, relative energy differences are quite 
OK, so you can determine an equilibrium volume. Meta-GGA gives you a 
better *absolute* value of the total energy, while all other 
properties (forces, efg, ...) are the same as in regular GGA.

Therefore, I think your observation that the effect of meta-GGA is 
only a shift in the total energy is what you can expect.

Stefaan


> Has anyone tried the meta-GGA options at all? By a process of
> elimination,
> I've worked out that it can be run after a normal GGA by doing "x
> mixer_vresp" to generate the case.vrespup/dn files, after copying
> case.inm
> to case.inm_vresp as described in the UG. However, except for a shift
> in
> the absolute energy is does not look like it's changed much if
> anything.
> Am I missing some additional information/files that are needed?
> 
> -----------------------------------------------
> Laurence Marks
> Department of Materials Science and Engineering
> MSE Rm 2036 Cook Hall
> 2225 N Campus Drive
> Northwestern University
> Evanston, IL 60201, USA
> Tel: (847) 491-3996 Fax: (847) 491-7820
> mailto:L-marks at northwestern.edu
> http://www.numis.northwestern.edu
> -----------------------------------------------
> 
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-- 
Stefaan Cottenier
Instituut voor Kern- en Stralingsfysica
K.U.Leuven
Celestijnenlaan 200 D
B-3001 Leuven (Belgium)

tel: + 32 16 32 71 45
fax: + 32 16 32 79 85
e-mail: stefaan.cottenier at fys.kuleuven.ac.be