[Wien] A basic question regarding structure optimization

[Peter Blaha]

It means that the calculated value for the lattice parameters is (more 
or less) wrong.

> As you have told sometimes "the error could be very large (giving you
> meaningless results)"
>
> Does it mean that we may run into a local minima instead of global
> minima...if the "error" is large?
>
> looking forward to your response.
>
> with regards,
>
>
> On Mon, Sep 23, 2013 at 11:36 AM, Peter Blaha
> <pblaha at theochem.tuwien.ac.at <mailto:pblaha at theochem.tuwien.ac.at>> wrote:
>
>     You CAN DO AND probably SHOULD ALWAYS DO a simultaneously
>     optimization of external (lattice parameters) and internal (atomic
>     positions) degrees of freedom with wien2k.
>     Just use MSR1a  in the   run_lapw  step in volume optimization or
>     replace run_lapw by min_lapw in any script.
>
>     The "error" could be small (or almost zero), or could be very large
>     (giving you meaningless results). This depends on your specific case.
>
>
>
>     On 09/23/2013 06:27 AM, shamik chakrabarti wrote:
>
>         Sir,
>
>                I have a basic question regarding the method of structure
>         optimization in wien2k.
>
>         If we optimize it in two  successive steps (i) first optimize
>         volume and
>         lattice parameters and then (ii) for structure having optimized
>         volume
>         and lattice parameters further optimization of structural
>         coordinates......
>
>         how much different (or how much erroneous !!) will be the final
>         optimize
>         structure in comparison to that obtained by simultaneous
>         variation of
>         lattice parameters and structural coordinates as can be done in
>         PAW code
>         VASP.
>
>         Any response in this regards will be very helpful for us. Thanks
>         in advance.
>
>         with regards,
>
>         --
>         Shamik Chakrabarti
>         Senior Research Fellow
>         Dept. of Physics & Meteorology
>         Material Processing & Solid State Ionics Lab
>         IIT Kharagpur
>         Kharagpur 721302
>         INDIA
>
>
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>
>     --
>
>                                            P.Blaha
>     ------------------------------__------------------------------__--------------
>     Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
>     Phone: +43-1-58801-165300             FAX: +43-1-58801-165982
>     Email: blaha at theochem.tuwien.ac.at
>     <mailto:blaha at theochem.tuwien.ac.at>    WWW:
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>     <http://info.tuwien.ac.at/theochem/>
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>
>
>
> --
> Shamik Chakrabarti
> Senior Research Fellow
> Dept. of Physics & Meteorology
> Material Processing & Solid State Ionics Lab
> IIT Kharagpur
> Kharagpur 721302
> INDIA
>
>
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-- 

                                       P.Blaha
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-165300             FAX: +43-1-58801-165982
Email: blaha at theochem.tuwien.ac.at    WWW: 
http://info.tuwien.ac.at/theochem/
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