[Pw_forum] Acceptable error in cohesive energy

[Duy Le]

>From my understanding, correct me if I am wrong.

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.
>
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>
>


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