<div dir="ltr">While there is some rationale to changing the angles to 90, this is in general not appropriate.<div><br></div><div>Rather than doing this I suggest working through the examples in the Wien2k documentation. There are also examples in the Lecture notes on the web page. This will teach you a lot.</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Thu, Apr 23, 2015 at 10:02 AM, delamora <span dir="ltr"><<a href="mailto:delamora@unam.mx" target="_blank">delamora@unam.mx</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">The simplest perivskite is<br>
a=b=c<br>
alpha=beta=gamma=90<br>
A: 1/2,1/2,1/2<br>
B: 0,0,0<br>
O: 1/2,0,0<br>
0,1/2,0<br>
0,0,1/2<br>
space group 221<br>
so, if you have alpha=89.999 you can adjust to 90.<br>
Now, if you have alpha=89.9 you can adjust to 90 for learning purposes, the calculation will be quite fast, but the final calculation you should use 89.9 and the pbnm group that has lower symmetry<br>
Pablo<br>
<br>
________________________________________<br>
De: <a href="mailto:wien-bounces@zeus.theochem.tuwien.ac.at">wien-bounces@zeus.theochem.tuwien.ac.at</a> <<a href="mailto:wien-bounces@zeus.theochem.tuwien.ac.at">wien-bounces@zeus.theochem.tuwien.ac.at</a>> en nombre de Víctor Luaña Cabal <<a href="mailto:victor@fluor.quimica.uniovi.es">victor@fluor.quimica.uniovi.es</a>><br>
Enviado: jueves, 23 de abril de 2015 07:54 a. m.<br>
Para: A Mailing list for WIEN2k users<br>
Cc: Victor Luaña<br>
Asunto: Re: [Wien] (no subject)<br>
<br>
On Thu, Apr 23, 2015 at 05:56:00PM +0530, Shakeel Khandy wrote:<br>
> I m a beginner and i want to study a compound of ABO3 type pervoskite with<br>
> space group *pbnm*.I have got confused with the atomic positions of<br>
> *pbnm *spacegroup.<br>
> Although the experimental atomic positions are in my hand,but the problem<br>
> lies in the negative atomic positions given by experimental data. Is there<br>
> any other method to have the required atomic positions.<br>
<br>
Shakeel,<br>
<br>
1) The crystallographic description of coordinates assumes periodicity.<br>
So x=-0.12 is identical to 1+x=1-0.12. Any crystallographer is trained<br>
to do the operation quickly and the easy way is thinking<br>
<br>
1 = 0.999999999(10)<br>
--------- as mant 9's as it is needed<br>
<br>
2) ¿Don't have a professor to traing you? ¿Don't have books on<br>
crystallography available?<br>
<br>
3) Assuming the answers are NO in both cases let me recommend<br>
you some materials appropriate to the level of your question<br>
<br>
a) My own slides on the subject<br>
<br>
<<a href="http://azufre.quimica.uniovi.es/DetEst/" target="_blank">http://azufre.quimica.uniovi.es/DetEst/</a>><br>
<br>
Sorry by the spanish. Use google translate as you need.<br>
<br>
b) An excellent and recent manual by italian crystallographers:<br>
<br>
C. Giacovazzo, Ed. Fundamentals of crystallography, IUCr & Oxford Univ Press<br>
IUCR: 0198555784, 1992<br>
<br>
There is a new edition, but I don't have it al hand.<br>
<br>
4) This type of question should be solved by your prof./teacher<br>
<br>
Good luck,<br>
Dr. Víctor Luaña<br>
--<br>
. . DEEP THOUGHT in D. Adams; Hitchhikers Guide to the Galaxy:<br>
/ `' \ "I think the problem, to be quite honest with you,<br>
/(o)(o)\ is that you have never actually known what the question is."<br>
/`. \/ .'\<br>
/ '`'` \ "Lo mediocre es peor que lo bueno, pero también es peor<br>
| \'`'`/ | que lo malo, porque la mediocridad no es un grado, es una<br>
| |'`'`| | actitud"<br>
\/`'`'`'\/ -- Jorge Wasenberg, 2015<br>
===(((==)))==================================+=========================<br>
! Dr.Víctor Luaña, in silico chemist & prof. ! Mediocre is worse than<br>
! Departamento de Química Física y Analítica ! good, but it is also<br>
! Universidad de Oviedo, 33006-Oviedo, Spain ! worse than bad, because<br>
! e-mail: <a href="mailto:victor@fluor.quimica.uniovi.es">victor@fluor.quimica.uniovi.es</a> ! mediocrity is not a grade,<br>
! phone: +34-985-103491 fax: +34-985-103125 ! it is an attitude<br>
+--------------------------------------------+<br>
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(being reworked)<br>
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</blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="gmail_signature"><div dir="ltr">Professor Laurence Marks<br>Department of Materials Science and Engineering<br>Northwestern University<br><a href="http://www.numis.northwestern.edu" target="_blank">www.numis.northwestern.edu</a><div>Corrosion in 4D: <a href="http://MURI4D.numis.northwestern.edu" target="_blank">MURI4D.numis.northwestern.edu</a><br>Co-Editor, Acta Cryst A<br>"Research is to see what everybody else has seen, and to think what nobody else has thought"<br>Albert Szent-Gyorgi</div></div></div>
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