[Wien] actual value of RKmax

[Andrei Postnikov]

Javad,

If you are serious about comparing the energies
of different systems/phases, you should of course try to increase
input RKmax in order to make sure
that the DIFFERENCE is energies you care about
has CONVERGED in RKmax (also GMax and k-mesh)
to the accuracy which is relevant to you;
once this happened, the exact input value of RKmax
is no more important.

Without such convergency, if you somehow enforce the same RKmax
for your compared phases, you'll have no guarantee how
accurate your energy difference will be.

Particularly in the volume optimization, one may sometimes get
kinks in the volume curve due to stepwise change of Kmax or Gmax
at some volumes; before comparing different phases, you should
increase the cutoffs enough to suppress such kinks.

Andrei

 +-- Dr. habil. Andrei Postnikov ----- Tel. +49-541-969.2377 -- Fax .2351 ---+
 | Universitaet Osnabrueck - Fachbereich Physik, D-49069 Osnabrueck, Germany |
 +-- apostnik at uos.de --------- http://www.home.uni-osnabrueck.de/apostnik/ --+

On Thu, 8 Apr 2004, Javad Hashemifar wrote:

| > actual value, of course.
|
| Thanks Kevin for the answer,
| But the problem is that durnig the volume-optimization we are are comparing the
| total energy of similar systems with different value of actual RKmax !!!
| however the input value of RKmax is the same for different vilumes.
|
| any other comments ??
| bests.
| Javad
|
| >
| > Kevin.
| >
| >
| > 	-----Oorspronkelijk bericht-----
| > 	Van: Javad Hashemifar [mailto:s_javad at yahoo.com]
| > 	Verzonden: do 4/8/2004 11:00
| > 	Aan: wien at zeus.theochem.tuwien.ac.at
| > 	CC:
| > 	Onderwerp: [Wien] actual value of RKmax
| >
| >
| >
| > 	Dear Wien Users,
| > 	I have a question about the meaning of "Actual RKmax"
| > 	It is clear that the total energy of two similar systems can be compared if
| > 	they were obtained using the same RKmax, however it is not clear that input
| > 	value of RKmax (in case.in1) should be the same or the Actual value of RKmax
| > 	(parameter :RKM in the scf file).
| > 	Any comments will be appreciated.
| >
| > 	Best regards,
| > 	Javad Hashemifar
| >
| > 	=====
| >
| >
| -------------------------------------------------------------------------------
| > 	Javad Hashemifar                                      phone : ++49-30-8413
| > 4804
| > 	Permanent : Physics Department, Isfahan University of Technology, Isfahan,
| > Iran
| > 	Current : Fritz-Haber-Institut der MPG, Faradayweg 4-6, D-14195 Berlin,
| > Germany
| > 	e-mails:  hashemi at fhi-berlin.mpg.de          &
| > hashemifar at ph.iut.ac.ir
| >
| >
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