[Wien] silicon structure

[Gerhard Fecher]

why are you giving two atoms for the basis of Si ?
Set up 2 (see Peters remark) of spacegroup 229 should have only one on Wyckoff position 8a.

did you recognize something from youre RMT sizes ?

I usually use this example for my students to check if they know about crystal structures and 
to find out how they turn semiconductors into metals

Ciao
Gerhard

====================================
Dr. Gerhard H. Fecher
Institut of Inorganic and Analytical Chemistry
Johannes Gutenberg - University
55099 Mainz
________________________________________
Von: wien-bounces at zeus.theochem.tuwien.ac.at [wien-bounces at zeus.theochem.tuwien.ac.at]" im Auftrag von "Jedo [jedokim at umich.edu]
Gesendet: Montag, 14. Juni 2010 12:35
An: wien at zeus.theochem.tuwien.ac.at
Betreff: Re: [Wien] silicon structure

Thanks for the answer. Still, I don't understand why WIEN2k is giving me
a structure with this many atoms. I'm listing the Strucgen atoms when I
save it. It adds 10 more atoms. The fractional coordinates look ok, but
when I look at the structure using Xcrysden, it does not look right. I
can send you the screen shot if you wish.
Thanks for all the help.

Space group 227_Fd-3m

a = 5.43 b = 5.43 c = 5.43
90 90 90

Atom 1 Si z = 14 RMT 1.21
          pos 1 x = 0.0 0.0 0.0
          pos 2 x = 0.0 0.25 0.25
          pos 3 x = 0.0 0.25 0.25
          pos 4 x = 0.0 0.25 0.25

Atom 2 Si x = 14 RMT 1.21
          pos 1  0.25 0.25  0.25
          pos 2  0.75 0.75  0.75
          pos 3  0.75 0.5    0.5
          pos 4  0.25 0.0    0.0
          pos 5  0.0   0.0    0.25
          pos 6  0.5   0.5    0.75
          pos 7  0.5   0.75  0.5
          pos 8  0.0   0.25  0.0




On 6/14/2010 12:59 AM, Peter Blaha wrote:
> Nothing is wrong.
> sgroup changes your input structure and shifts the origin to an
> inversion center. This moves the Si atoms by (1/8,1/8,1/8).
>
> PS: The spacegroup 227 has 2 different "settings", i.e. origins with
> tetrahedral symmetry or with inversion symmetry. Since all matrix
> elements
> can be kept as "real" numbers when inversion symmetry is present, WIEN2k
> adopts automatically this setting.
>
> Jedo schrieb:
>> Hi,
>>
>> I'm a newbie to wien2k. I have done some abinit calculation with
>> silicon. So, I just wanted to start with Silicon again to test it.
>> However, when I put the structure in, it gives me a very different
>> structure. I'm not sure what I am doing wrong. My inputs for
>> StructGen for Silicon is
>>
>> Spacegroup 227_Fd-3m
>> Lattice parameters A 5.43 5.43 5.43
>> 90 90 90
>>
>> Si  0 0 0
>> Si 0.25 0.25 0.25
>>
>> Is this correct? I'm used to inputing lattice vectors.
>> Thanks for the help
>>
>> Jedo
>>
>

--
================================
Jedo Kim, Ph.D Candidate
Heat Transfer Physics Laboratory
2350 Hayward, 2186 GG Brown Bldg.
University of Michigan, Ann Arbor, MI 48109-2143
Email: jedokim at umich.edu, jdzbox at hotmail.com
Tel: 734-764-3487 (o); 734-276-8370 (cell)
http://sitemaker.umich.edu/kaviany
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