# [Wien] Representative number for O2 energy

L. D. Marks L-marks at northwestern.edu
Fri Mar 11 18:41:02 CET 2005

```On Fri, 11 Mar 2005, Veronica Ganduglia Pirovano wrote:

>
> I would  do exactly that see PRB 59, 15533 (1999)
> I suggest an even higher cut off (30 Ry, at least!) for E_a and E_b.
> I used 24 Ry and I know now that a somewhat larger cutoff gives an even
> larger
> number for the atomization energy.  The expected number is approx 3.1
> eV/atom.
> O has to be calculated in a NON-cubic box!  to get the right occupation!
Can you expand slightly on this comment; it might be useful for
others (maybe I'm just being thick but I don't see why immediately).

N.B., thanks also to Jeff Spirko. Extending his concept, one (I) could
calculate the E as a function of distance to do a extrapolation.
>
>
> L. D. Marks wrote:
>
> >I would like to get a representative energy (i.e. not the correct one, but
> >one which is consistent with other calculations) for the O2 (molecule)
> >energy for an RMT of 1.6 and RKMAX of 7, GGA. (These values are what I am
> >using in some other calculations of bulk oxides, and the energy of O2
> >has a significant effect on the theoretical heats of formation.) Obviously
> >I cannot use these for the O2 molecule, the RMT has to be about 1.1. What
> >I have done is:
> >	a) Calculate O2 with RMT=1.1 RKMAX=5, ~30 a.u. cell: E_a
> >	b) Calculate O  with RMT=1.1 RKMAX=5, ~30 a.u. cell: E_b
> >	c) Calculate O  with RMT=1.6 RKMAX=7, ~30 a.u. cell: E_c
> >Then estimate the effective O2 energy as
> >	E_a - 2*E_b + 2*E_c
> >
> >I would be interested to know if anyone has a better idea/method, apart
> >from using 2*E_c + an experimental number for the bond energy (or
> >meta-GGA).
> >
> >-----------------------------------------------
> >Laurence Marks
> >Department of Materials Science and Engineering
> >MSE Rm 2036 Cook Hall
> >2220 N Campus Drive
> >Northwestern University
> >Evanston, IL 60201, USA
> >Tel: (847) 491-3996 Fax: (847) 491-7820
> >email: L - marks @ northwestern . edu
> >http://www.numis.northwestern.edu
> >-----------------------------------------------
> >
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> >
> >
>
>
> --
> ------------------------------------------------------------
>             Dr. M. Veronica Ganduglia-Pirovano
> 	    Humboldt-Universitaet zu Berlin
> 	    Institut fuer Chemie
> Post:   Unter den Linden 6
>           10099 Berlin
>
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>
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-----------------------------------------------
Laurence Marks
Department of Materials Science and Engineering
MSE Rm 2036 Cook Hall
2220 N Campus Drive
Northwestern University
Evanston, IL 60201, USA
Tel: (847) 491-3996 Fax: (847) 491-7820
email: L - marks @ northwestern . edu
http://www.numis.northwestern.edu
-----------------------------------------------

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