[gpaw-users] FD vs LCAO vs PW

[Michael Walter]

Dear Ask,

would it be possible to put your nice summary to the gpaw-web pages ? This
could be useful for others and such thinks are not easy to find in email
conversations.

Best,
Michael


2014-06-30 21:53 GMT+02:00 Ask Hjorth Larsen <asklarsen at gmail.com>:

> Hi Robert!
>
> Generally:
>
> LCAO has the advantage over FD/PW that it's fast for larger systems since
> you have fewer degrees of freedom in the diagonalization.
>
> FD/PW have the advantage over LCAO that it's easy to crank up the
> precision by setting grid spacing or planewave cutoff.
>
> PW has the advantage over FD that planewaves are "nice" (they tend to
> better represent wavefunctions) and you need less to have a reasonable
> representation.  Also the planewaves don't suffer egg-box effect like grid
> points do.  Apparently stuff like response calculations are much nicer in
> PW mode.
>
> FD has the advantage over PW that you can throw many CPUs at domain
> decomposition.  In PW, you can only parallelize over k-points/spins/bands.
> If you want do do many hundreds of atoms, PW would therefore be less useful.
>
> PW is extremely efficient for small-ish periodic systems.
>
> In GPAW specifically:
>
> PW has the slight disadvantage that it's new-ish and thus more prone to
> things not working.
>
> I think PW is still the only mode that implements the stress tensor.
>
> LCAO has the slight disadvantage that it's quite different from the two
> other modes, and e.g. some advanced functionals have not been implemented
> with LCAO.
>
> LCAO is very inefficient for systems where the cell is smaller than the
> basis functions.
>
> Did I leave anything out?  Any questions?
>
> Best regards
> Ask
>
>
>
> 2014-06-30 17:48 GMT+02:00 Robert Warmbier <Robert.Warmbier at wits.ac.za>:
>
>>  Dear GPAW users and developers,
>>
>> I was wondering if someone could provide a comparative pro/con list for
>> the different modes GPAW supports. There is very little information on the
>> GPAW website, as far as I could find.
>> If there is already information and I missed it, I am sorry.
>>
>> Best Robert
>>
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PD Dr Michael Walter
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