[Wien] silicon structure

[Jedo]

Thanks,

That worked.

Now, that is taken care of, I still have another puzzling situation. I 
want to make a 2*2*2 super cell of Silicon.
If I repeat the steps
Type "F" Then specify Si atoms using fractional coordinates (should be 
16 atoms in total, I used material studio to visualize it is correct and 
transfer the coordinates to WIEN2K). I do not get are larger diamond 
structure. Can you explain why this is?
Thanks.

Jedo


Peter Blaha wrote:
>> You mean Wyckoff position 8a as (0, 0, 0) right? I tried that before,
>
> No, we mean the second setting and for this setting the coordinates of
> position 8a are (1/8,1/8,1/8).
>
> Alternatively, just use instead of the spacegroup the latrtice type "F"
> and specify the Si atoms at (0,0,0) and (.25,.25,.25)
>
> During initialization, sgroup should complain and generate a struct file
> compatible with WIEN2k.
>
> PS: I remember that I was quite confused myself as young researcher, 
> that the common spacegroup-symbol + Wyckoff position is not 
> necessarily sufficient to define a structure, but there are 2 
> different settings.
>
>
>
>
>> 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
================================