[Wien] silicon structure

[Jedo]

Hi there,

You mean Wyckoff position 8a as (0, 0, 0) right?  I tried that before, 
but the structure I see using Xcrysden was even more wrong. If I do 
that, the file looks like

Space group 227_Fd-3m

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

Atom 1 Si z = 14 RMT 1.8
           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

It is a big change for me to work with space groups from lattice vectors.


For RMT sizes, I could not increase them because of the error I get from 
the first step (x nn). I'm thinking that I am getting these errors 
because my structure is not correct. Also, even though I increase them, 
when I hit "set automatically RMT" it reduces it back to 1.8.



On 6/14/2010 7:11 AM, Gerhard Fecher wrote:
> 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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>
>    

-- 
================================
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
================================