[Wannier] Wannier Digest, Vol 59, Issue 4

[Angelo Ziletti]

Dear Nicola,
you were right, my disentanglement window was too small and it wasn't able to capture all the dispersion of the bands I am interested in.
Now it works nicely.
Thanks for your advice.
Best,
Angelo

> Angelo Ziletti
> PhD Candidate - School of Physics 
> University College Dublin
> angelo.ziletti at gmail.com


On 4 Oct 2012, at 09:05, wannier-request at quantum-espresso.org wrote:

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> Today's Topics:
> 
>   1. Constraint centers positions and disentanglement check	point
>      (Angelo Ziletti)
>   2. Re: Constraint centers positions and disentanglement check
>      point (Nicola Marzari)
> 
> 
> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Wed, 3 Oct 2012 15:20:58 +0100
> From: Angelo Ziletti <angelo.ziletti at gmail.com>
> Subject: [Wannier] Constraint centers positions and disentanglement
> 	check	point
> To: wannier at quantum-espresso.org
> Message-ID: <8FCF984D-EAD6-46D7-8082-DF20A8DECA39 at gmail.com>
> Content-Type: text/plain; charset=us-ascii
> 
> Dear WannierUsers,
> I am using Wannier90 to get parameters for a tight-binding Hamiltonian.  My system consists of a polymer on top of a graphene sheet.
> I got the MLWFs for the graphene and the polymers (separated).
> I want to calculate the hopping integrals between the MLWFs of the polymer and the MLWFs of the graphene; so, I did the electronic structure with polymer and graphene together.
> I have lots of trouble to get the MLWF centers in meaningful positions (i.e. right symmetries)  and the right band structure interpolation. 
> 
> So, I have two questions:
> 1) how can I constraint the position of the Wannier Functions during the spread minimization procedure? (namely, I want to use the information from the separate calculations - the graphene-polymer interaction is weak)
> 2) how can I put a check-point in the disentanglement? (the disentanglement is taking very long)
> 
> Thanks for your attention.
> 
> Angelo Ziletti
> PhD Candidate - School of Physics 
> University College Dublin
> angelo.ziletti at gmail.com
> 
> 
> 
> 
> ------------------------------
> 
> Message: 2
> Date: Wed, 03 Oct 2012 18:09:20 +0200
> From: Nicola Marzari <nicola.marzari at epfl.ch>
> Subject: Re: [Wannier] Constraint centers positions and
> 	disentanglement check point
> To: Angelo Ziletti <angelo.ziletti at gmail.com>
> Cc: wannier at quantum-espresso.org
> Message-ID: <506C6330.1020000 at epfl.ch>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> 
> 
> 
> Dear Angelo,
> 
> 
> for the combined system, are you using centers and projectors that
> match as closely as possible the ones you found for the two separated
> systems?
> 
> If the case, my only guess is that you might have used a disentanglement
> window that is too small. Try to look at the separate and the combined
> band structures, to get a sense what states you should be spanning.
> 
> In general, there shouldn't be a lot of chemistry or charge transfer 
> going on in your system, so what you get in the spearated case should be
> a very good starting point.
> 
> With regards to your questions, 1) is something that we should 
> implement, sooner or later. Conceptually, it means minimizing the
> expectation value of (r-rfixed)^2, i.e. <r^2> -2<r>rfixed - so
> it's a matter of regrouping terms and updating the gradient.
> 
> Re 2), I do not think there is any runtime flag that one could
> use, but (if not) maybe we should consider for the future having
> the possibility of re-tuning on-the-fly the wannier parameters.
> 
> 
> 			nicola
> 
> 
> On 03/10/2012 16:20, Angelo Ziletti wrote:
>> Dear WannierUsers,
>> I am using Wannier90 to get parameters for a tight-binding Hamiltonian.  My system consists of a polymer on top of a graphene sheet.
>> I got the MLWFs for the graphene and the polymers (separated).
>> I want to calculate the hopping integrals between the MLWFs of the polymer and the MLWFs of the graphene; so, I did the electronic structure with polymer and graphene together.
>> I have lots of trouble to get the MLWF centers in meaningful positions (i.e. right symmetries)  and the right band structure interpolation.
>> 
>> So, I have two questions:
>> 1) how can I constraint the position of the Wannier Functions during the spread minimization procedure? (namely, I want to use the information from the separate calculations - the graphene-polymer interaction is weak)
>> 2) how can I put a check-point in the disentanglement? (the disentanglement is taking very long)
>> 
>> Thanks for your attention.
>> 
>> Angelo Ziletti
>> PhD Candidate - School of Physics
>> University College Dublin
>> angelo.ziletti at gmail.com
>> 
>> 
>> _______________________________________________
>> Wannier mailing list
>> Wannier at quantum-espresso.org
>> http://www.democritos.it/mailman/listinfo/wannier
>> 
> 
> 
> -- 
> 
> ----------------------------------------------------------------------
> Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL
> 
> 
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> End of Wannier Digest, Vol 59, Issue 4
> **************************************