[gpaw-users] LCAO mode for Zeolite

[Juho Arjoranta]

Lainaus "Ask Hjorth Larsen" <asklarsen at gmail.com>:

> Dear Baldissin
>
> 2012/7/12 baldissin <baldissin at yahoo.it>:
>> Dear gpaw users
>>
>> I am calculating the site preference of Al substitution in zeolite.
>> Unit cells are massive ( 20x20x13 Ang ). My idea is using LCAO mode.
>> I am wondering if the method is accurate enough to discriminate energy
>> with difference of some meV (5-20).
>> any opinion?
>>
>> thanks a lot
>> Gael
>>
>> PS:   calc = GPAW( mode='lcao' ,  h=0.18, nbands=-5, xc='PBE',
>> txt='atoms.out', kpts=[(0, 0, 0)], usesymm=True , charge=-1,
>> maxiter=150   )
>
> Energies in LCAO mode are usually off quite significantly.  However
> trends are reproduced very well in my experience.  You may need to do
> it the hard way and compare to some grid-based calculations.
>
> Be sure to follow the advice for optimizing the performance of the
> Poisson solver in such a large system:
> https://wiki.fysik.dtu.dk/gpaw/documentation/lcao/lcao.html#notes-on-performance
>
> (Don't reduce the solver's tolerance, but make sure the number of grid
> points is divisible with a high power of 2).
>
When parallelizing over domain should the number of grid points be  
divisible with a high power of 2 in the whole system or in the boxes  
that the system is divided into?
>
> You don't need to specify kpts and usesymm above.  You will need
> basis='dzp' set if you want sensible numbers though.
>
> Regards
> Ask
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