[Wien] Relaxation of already known structure

[Víctor Luaña Cabal]

On Mon, Jul 21, 2014 at 02:16:27PM -0500, Jihoon Park wrote:
> I am wondering if we must do the relaxation for all calculations.
> I have found some first principles studies with experimental lattice
> constants, including Dr. Novak's work "PRB 71, 1844422 (2005)."
> Therefore, I need to know if the first principles calculations with
> experimental lattice constants are reliable or in what case, it is good
> enough or somethings.
> Could anybody please give me some guidance?

It depends very much on your intention. Optimizing an structure can be
taken as a test of how appropriate is your calculation method for the
system you are trying to analyze. The experimental value is the thing
you are trying to reproduce, but not all experiments are done under
the same precision, nor all experiments provide a well defined result.

Remember that science is understanding, not only producing tables
of numbers. Very simple models have been fundamental in science.
For instance we owe our periodic table of the elements basically to
ideas and concepts generated before quantum mechanics.

It is not wrong, of course, the use a simple well defined recipe on a
large collection of compounds trying to get some systematic rule.

So, try to learn from the literature in your field and try to follow
an unexploited road from the best starting point. Not a simple way but
remember: It is easy to imagine a simple solution for a complex problem
... the pity is that most are wrong!

Best regards,
             Dr. Víctor Luaña

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       \|/a  "After years of working on a problem the genius shout:
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