No subject

DFT-Cohesive energy is decided by the functional and the pseudo-potential.
If the pseudo-potential and the functional predict correctly the ground
state of isolated atom and the bulk, we usually get less than 10% error.
This is the case of Al with GGA (I believe). For some other, especially in
transition metal where the ground states of isolated atoms (and/or bulks)
are not well predicted within DFT, the error in cohesive energy could be 20%
or more.
When a pseudo-potential is generated, it must be well tested before
releasing. It's safe to use.

On Wed, Sep 16, 2009 at 2:19 AM, udayagiri sai babu <udayagiri3 at gmail.com>wrote:

> Dear PWSCF users
> I calculated the cohesive energy for aluminium using GGA potential, which
> came out to be 3.59 ev/atom. When i compared this value with that of given
> in Kittel (3.34ev/atom) the error is 7.5%. Here i would like to know how
> much error in cohesive energy is acceptable and also if somebody can comment
> on error tolerance in lattice parameter and Bulk modulus (for GGA as well as
> LDA) as well it would be nice.
> Thanks in advance
>
> --
> U.Saibabu
> PhD student,
> Deformation mechanisms modeling group,
> Materials engineering department,
> IISc Bangalore,
> India.
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum
>
>


-- 
--------------------------------------------------
Duy Le
PhD Student
Department of Physics
University of Central Florida.

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<div>From my understanding, correct me if I am wrong.</div><div><br></div>D=
FT-Cohesive energy is decided by the functional and the pseudo-potential. I=
f the pseudo-potential and the functional predict correctly the ground stat=
e of isolated atom and the bulk, we usually get less than 10% error. This i=
s the case of Al with GGA (I=A0believe). For some other, especially in tran=
sition metal where the ground states of isolated atoms (and/or bulks) are n=
ot well predicted within DFT, the error in cohesive energy could be 20% or =
more.<div>

<br></div><div>When a pseudo-potential is generated, it must be well tested=
 before releasing. It&#39;s safe to use.<br><br><div class=3D"gmail_quote">=
On Wed, Sep 16, 2009 at 2:19 AM, udayagiri sai babu <span dir=3D"ltr">&lt;<=
a href=3D"mailto:udayagiri3 at gmail.com">udayagiri3 at gmail.com</a>&gt;</span> =
wrote:<br>

<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex;">Dear PWSCF users<br>I calculated the cohesi=
ve energy for aluminium using GGA potential, which came out to be 3.59 ev/a=
tom. When i compared this value with that of given in Kittel (3.34ev/atom) =
the error is 7.5%. Here i would like to know how much error in cohesive ene=
rgy is acceptable and also if somebody can comment on error tolerance in la=
ttice parameter and Bulk modulus (for GGA as well as LDA) as well it would =
be nice.<br>


Thanks in advance<br clear=3D"all"><font color=3D"#888888"><br>-- <br>U.Sai=
babu<br>PhD student,<br>Deformation mechanisms modeling group,<br>Materials=
 engineering department,<br>IISc Bangalore,<br>India.<br>
</font><br>_______________________________________________<br>
Pw_forum mailing list<br>
<a href=3D"mailto:Pw_forum at pwscf.org">Pw_forum at pwscf.org</a><br>
<a href=3D"http://www.democritos.it/mailman/listinfo/pw_forum" target=3D"_b=
lank">http://www.democritos.it/mailman/listinfo/pw_forum</a><br>
<br></blockquote></div><br><br clear=3D"all"><br>-- <br>-------------------=
-------------------------------<br>Duy Le<br>PhD Student<br>Department of P=
hysics<br>University of Central Florida.<br>
</div>

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