The ABINIT Users Mailing List ( CLOSED )

["Anglade Pierre-Matthieu" <anglade@gmail.com>]

Hi,

By "nonsense" Ian Haiping probably means that it has no sense : energy
is defined up to a constant and knowing the total energy of a system
without any clues about the constant is not very informative.
Actually, even in our case where the constant is well known total
energy is not meaningfull. Especially if you don't know exactly what
you are computing.
Sensible information is borne by gradients of energy. For instance
derivative with respect to lattice change or atomic displacement. If
you take the time to learn using Abinit and Wien you will likely find
very similar results with both for most most sensible calculations you
can perform (eg: lattice parameters, stresses, forces, phonons, etc).
Yet because you will always have different constant to define your
energy (plus all slight differences arising from physical
approximation and numerical methods) the total energy of two similar
system are quite unlikely to come close one to the other.

regards

PMA

On Fri, May 16, 2008 at 7:40 PM, zoulikha charifi <charifi_z@yahoo.fr> wrote:
>  Dear lan haiping
>  thanks for your answer.  What do you mean by the absolute value of total 
> energy is nonsense?
>
>
>
>
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-- 
Pierre-Matthieu Anglade