[Wien] silicon structure

[Peter Blaha]

> 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
>> ================================
>>
>> _______________________________________________
>> Wien mailing list
>> Wien at zeus.theochem.tuwien.ac.at
>> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>> _______________________________________________
>> Wien mailing list
>> Wien at zeus.theochem.tuwien.ac.at
>> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>>
>>
>

-- 
Peter Blaha
Inst.Materialchemie, TU Wien
Getreidemarkt 9
A-1060 Vienna
Austria