[Wien] [Wien2k Users] Lattice Stability usingStructure Optimization

[Ghosh SUDDHASATTWA]

Thanks Stefaan for the reply. 
I guess I am better off by considering only Option 2 for hcp cases. I am
feeling a bit nervous to choose other options in the optimization procedure.

Yes, it is quite true that there are I in fact two variables; volume and
c/a. 
I got a pretty good variation in energy and c/a. 
But I know it is not a complete study. 
Probably we have to vary volume and c/a simultaneously (2D Optimize) so that
we get all possibilities. 

Suddhasattwa Ghosh 


-----Original Message-----
From: wien-bounces at zeus.theochem.tuwien.ac.at
[mailto:wien-bounces at zeus.theochem.tuwien.ac.at] On Behalf Of Stefaan
Cottenier
Sent: Tuesday, March 23, 2010 1:11 PM
To: A Mailing list for WIEN2k users
Subject: Re: [Wien] [Wien2k Users] Lattice Stability usingStructure
Optimization


Now read Martins mail again, and consider what he writes about enlarging 
the lattice constants (i.e. increasing the volume of the cell). Then, 
ponder what it means that you have 2 degrees of freedom here: a and c, 
or alternatively, volume and c/a.

Stefaan


Ghosh SUDDHASATTWA wrote:
> Dear Martin, 
> Probably I am responding to your mail after a long time. And moreover, you
> are absolutely correct. 
> If Pu is imagined to be in the Zr atomic positions, it is very natural
that
> the occupation of Pu would naturally increase the c/a ratio  and there is
no
> meaning to do a structure optimization for cases like -2 % or -5 % change
in
> c/a ratio. The equilibrium c/a would be somewhere around +12-15 % change
> (gross)  and this is what is expected from physics. 
> That is what I get from Wien2k 
> 
> Thanks Stefaan and Martin, 
> 
> Suddhasattwa Ghosh 
> 
> 
> -----Original Message-----
> From: wien-bounces at zeus.theochem.tuwien.ac.at
> [mailto:wien-bounces at zeus.theochem.tuwien.ac.at] On Behalf Of Martin
Pieper
> Sent: Tuesday, March 02, 2010 6:32 PM
> To: A Mailing list for WIEN2k users
> Subject: Re: [Wien] [Wien2k Users] Lattice Stability using
> StructureOptimization
> 
> Dear Ghosh Suddhasattwa,
> 
> being a beginner with Wien2k myself and not having read your exchange with

> Stefaan I probably should be quiet to avoid confusion but maybe its
simple: 
> Did you adapt (enlargen) the lattice constant when you put in Pu instead
of 
> Zr? I would expect that Pu needs a lot more space than Zr and, therefore,
> you 
> might simply be too far away from any reasonable lattice constant and far
> out 
> of the trial range of the optimization procedure...
> 
> Best regards,
> 
> Martin
> 
> 
> Am Montag, 8. März 2010 schrieb Ghosh SUDDHASATTWA:
>> Dear Dr.Stefaan,
>>
>> Coming back to the problem we discussed regarding lattice stability a few
>> days back, I have done a few things but am not able to proceed further.
>>
>> I imagine Pu in a Zr lattice (hcp, space group 194)
>>
>> There is only one equivalent position (0.3333333 0.666667 0.25)
>>
>> I replaced Zr atom with the Pu atom.
>>
>> My approach was the following
>>
>> 1.	Calculate ENE without spin orbit and with spin orbit
>> 2.	Structure optimization (Option 5)
>>
>>
>>
>> The ENE without spin orbit was -118767.962 Ry and with spin orbit was
>> -118769.097 Ry.
>>
>> I chose Option 5 for the structure optimization and it created 16
> different
>> struct files.
>>
>> Optimize.job was run and it did not give any errors. (Removed # from x
>> dstart only)
>>
>> When I chose energy vs volume in plot; it gave a linear variation and not
>> like what is given in the UG guide for TiC.
>>
>> Can you please tell me if I have done any mistake?
>>
>>
>>
>> Suddhasattwa Ghosh
> 
> 
> 


-- 
Stefaan Cottenier
Center for Molecular Modeling (CMM)
Ghent University
Technologiepark 903 (2nd floor)
BE-9052 Zwijnaarde
Belgium

http://molmod.Ugent.be
email: Stefaan . Cottenier /at/ UGent . be
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