[Wien] Guidance require for structure generation
Michael Sluydts
Michael.Sluydts at UGent.be
Fri Jul 4 12:04:50 CEST 2014
Hello Naseem,
The problem you have is a lack of information. The spacegroup and
stoichiometry still give you freedom through wyckoff positions to create
a variety of structures.
There are multiple avenues you can take. The first is to search the
literature and databases (COD: http://www.crystallography.net and ICSD
if you have access to it http://www.fiz-karlsruhe.com/icsd_home.html),
though I did not immediately find anything of interest in COD. If you
cannot find the structure then it becomes a different problem, rather
than determining materials properties you will have to do structure
prediction.
Structure prediction is a discipline in itself (literature available)
and can take a lot of time. If you know of similar compounds you may be
able to base yourself on them as a starting point to reduce your search
space, then try a few different configurations for the atoms, optimize
your cells and see what is lowest in energy.
Other more advanced methods are things like genetic algorithms where you
try different structures then combine them and gradually converge to a
candidate for the optimal structure. Software like USPEX exists for this
but I don't think it has been used with wien2k, though interfacing with
it should not be entirely impossible.
Trying to get more details on what you might be looking for is going to
be the first step either way.
Good luck,
Michael Sluydts
Naseem Hassan schreef op 4/07/2014 11:53:
> Thank You All.
>
> I benefited from all of you on mailing list. You are absolutely right
> I should learn instead of spoon feeding. I can understand fully that
> experts are already handling the burden of below average questions.
>
> Inspite of all your recommendation I wish that someone should suggest
> a road map of topics that leads to solution of making new structure in
> WIEN2k. I see many emails on mailing list that suggest the similar
> kind of problem of making structure for a specific space group. I
> really wanted to learn this but always lost in multiple topics. Many
> of seniors to whom I know personally know can not solve this problem.
> Just suggesting, that it will beneficial for newcomers if someone can
> prepare a tutorial on this issue. We sometimes do not work on
> compounds just because we cannot make structure file in wien2k.
>
> Best Regards
> Naseem
>
>
>
> On Fri, Jul 4, 2014 at 1:16 PM, Juan Manuel Perez Mato
> <wmppemam at lg.ehu.es <mailto:wmppemam at lg.ehu.es>> wrote:
>
> Please, learn some elementary crystallography in the International
> year of crystallography.
>
> regards,
>
> J. Manuel Perez-Mato
> Fac. Ciencia y Tecnologia,
> Universidad del Pais Vasco, UPV
> 48080 BILBAO,
> Spain
>
> tel. +34 946012473 <tel:%2B34%20946012473>
> fax. +34 946013500 <tel:%2B34%20946013500>
> ***************************************************
>
> El 04/07/2014, a las 02:37, Naseem Hassan escribió:
>
>> Dear Sir,
>>
>> Every space group has some ideal positions. From little
>> experience in the past, I believe on selecting 3 atoms in the
>> start of structure generation and assigning positions for three
>> atoms will give the primitive cell for this space group. In this
>> primitive cell other positions appear automatically by Wien2k.
>> Does a space group has not ideal positions ?. I need ideal
>> positions for three atoms and then I will relax the structure to
>> actual positions for this compound. Modeling a material is
>> possible without experimental results. I am hopeful that you will
>> propose some kind of solution.
>>
>> Thank you
>> Best Regards
>> Naseem Hassan
>>
>>
>>
>>
>> On Fri, Jul 4, 2014 at 1:22 AM, Peter Blaha
>> <pblaha at theochem.tuwien.ac.at
>> <mailto:pblaha at theochem.tuwien.ac.at>> wrote:
>>
>> Without atomic positions one cannot create a structure.
>>
>> Am 03.07.2014 19:46, schrieb Naseem Hassan:
>>
>> Dear Wien2k experts
>>
>> I am reporting this difficulty after going through
>> mailing list and
>> literature review. Kindly guide how can I generate
>> structure file with
>> the following information.
>>
>> Compound Formula: V3S7Cl
>> Space Group: C mmm#65 Orthorhombic
>> lattice parameters: a=20.6 b=3.8, c=3.9
>>
>> I need *general structure file* for this compound I will
>> try to remove
>> error associated with RMTs and other initializing
>> parameters by my self.
>>
>> Alternatively,
>>
>> If I select 3 atoms in the structure generation and I
>> insert all the
>> parameters as stated above then I just miss the position
>> of three atoms
>> in the structure file. In order to fill the positions I
>> checked the
>> wycoff psoitions from the Bilbao Crystallographic server
>> but I am unable
>> to understand which position should I give. *If this
>> approach is
>> correct* then kindly just *provide the positions* which I
>> can fill at
>> least ideal positions for this kind of space group so
>> that I can fill
>> and later on I will relax my structure to get actual
>> positons. Kindly do
>> guide.
>>
>> Best Regards
>> Naseem Hassan
>>
>>
>>
>>
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>>
>> --
>> Peter Blaha
>> Inst.Materials Chemistry
>> TU Vienna
>> Getreidemarkt 9
>> A-1060 Vienna
>> Austria
>> +43-1-5880115671 <tel:%2B43-1-5880115671>
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