[Wien] what mesh (real space) is used in WIEN2k? (Artem Urubkov)

[auru]

wrzttaa> Message: 6
wrzttaa> Date: Thu, 26 Aug 2004 15:22:30 +0300
wrzttaa> From: auru <auru at imp.kiev.ua>
wrzttaa> Organization: IMP
wrzttaa> To: "wien-request at zeus.theochem.tuwien.ac.at" <wien at zeus.theochem.tuwien.ac.at>
wrzttaa> Subject: [Wien] what mesh (real space) is used in WIEN2k? (Artem Urubkov)
wrzttaa> Reply-To: wien at zeus.theochem.tuwien.ac.at

wrzttaa>  Dear WIEN users! Reading UG, I saw that logariphmic mesh is used.
wrzttaa> Could you explain me, where is it used and what kind of mesh is used
wrzttaa> in interstitial? And also how dense is it in interstitial and what is
wrzttaa> the rule of generating the mesh?
wrzttaa>  Thanks a lot.
wrzttaa>                                      Artem Urubkov.


wrzttaa> --__--__--

wrzttaa> Message: 7
wrzttaa> From: Fred Nastos <nastos at physics.utoronto.ca>
wrzttaa> To: wien at zeus.theochem.tuwien.ac.at
wrzttaa> Subject: Re: [Wien] what mesh (real space) is used in WIEN2k? (Artem Urubkov)
wrzttaa> Date: Thu, 26 Aug 2004 08:49:19 -0400
wrzttaa> Reply-To: wien at zeus.theochem.tuwien.ac.at

wrzttaa> On August 26, 2004 08:22 am, auru wrote:
>>  Dear WIEN users! Reading UG, I saw that logariphmic mesh is used.
>> Could you explain me, where is it used

wrzttaa> I'm not sure what you mean by "where is it used"?  Where in
wrzttaa> the code, or where in the unit cell.  A logarithmic mesh is used
wrzttaa> in the "muffin-tin" region, which are spherical.  This is discussed
wrzttaa> in the user guide, and is the standard mesh that is used (90%
wrzttaa> of all atomic physics codes I have seen use an
wrzttaa> exponential/logarithmic mesh).  

wrzttaa> If you asked, where in the code is it used?  Lots of places.  Look
wrzttaa> in outwin.f (in many SRC_lapw1/) for example.

>> and what kind of mesh is used in interstitial?

wrzttaa> No real-space mesh is used in the interstitial. A plane-wave basis
wrzttaa> is used.

>> And also how dense is it in interstitial and what is
>> the rule of generating the mesh?

wrzttaa> The number of plane waves used is determined by gmax.  This
wrzttaa> is discussed at length in the userguide.

wrzttaa> Read the user guide, and the references therein.

 Dear WIEN users!
 I did following experiment. I created two .struct files for Ni2MnGa
(cubic fcc, 225 symmetry spacegroup) with equal arrangements of atoms,
equal MT-radia, equal RKmax and all other parameters, but: for one
case I set the lattice parameter 5.85A, and for another case the
lattice parameter was 15A. To my mind, the result was not obvious: the
calculation time for the second case became above 100 times greater
than for the first case. How to explain it? The numders of k-points in
IBZ for both of these cases are equal (10), gmax and Kmax are equal
too-- so, according to accessfull for me UGs (WIEN UG and "DFT and
the Family of (L)APW-methods: a step-by-step introduction"), matrixes
of expansion of wave functions must be equal by size and the
calculation times must be equal. If no meshes are used in real space
than I must have been mistaked. And, as far as I know,
"Gmax"-parameter is to control potential expansion in WIEN-code.
 Tell me, please, where is the mistake?