[CP2K-user] [CP2K:19515] Switching from GPW to GAPW

[Marcella Iannuzzi]

Dear Leon,

Yes you should probably use better basis sets. 
The Basis Set Exchange at https://www.basissetexchange.org offers a range 
of suitable options, some of which are already available in the 
EMSL_BASIS_SETS file.
One advantage of GAPW is the reduced PW cutoff necessary 

Regards
Marcella
On Tuesday, November 14, 2023 at 12:04:06 PM UTC+1 Léon Luntadila Lufungula 
wrote:

> Dear Prof. Hutter,
>
> Thanks for pointing me into the right direction!
>
> Unfortunately, the defaults are not sufficient for my system as I am 
> getting rather large values for the lines you suggested to check:
>
> (Inner SCF loop 1)
>   Total charge density (r-space):                      0.0000427891
>   Total Rho_soft + Rho0_soft (g-space):         0.0001310539
> (Inner SCF loop 2)
>   Total charge density (r-space):                      0.0000494000
>   Total Rho_soft + Rho0_soft (g-space):         0.0001376711
>
> I have attached my input file and the short part that was written to the 
> output if you would like to see it in more detail. My system consists of a 
> TiO2 [anatase (101)] slab with organic molecules adsorbed onto the surface, 
> so I suspect that it might be the Ti atoms for which the defaults are 
> insufficient.
>
> I have been looking into GAPW in the regtests, documentation and forum 
> over the last couple of days and from what I understand, the most important 
> parameters to change should be the following:
> (FORCE_EVAL / SUBSYS / KIND)
>
>    - *LEBEDEV_GRID*: I'm a bit unsure how to get a correct value for this 
>    parameter for each atom kind. Does this involve a convergence test for each 
>    atom type individually or is there some rule of thumb?
>    - *RADIAL_GRID*: same as for LEBEDEV_GRID.
>
> (FORCE_EVAL /DFT / QS)
>
>    - *EPS_DEFAULT*: This one is already at 1.0E-12, should I reduce it 
>    further?
>    - *EPS_FIT*: The default is 1.0E-4, but I've read in another post in a reply 
>    from M. Krack 
>    <https://groups.google.com/g/cp2k/c/FUvjXq9RvWY/m/8VwHvHGUAgAJ> that 
>    it is too large for most systems and should be reduced to 1.0E-6. Should I 
>    reduce it in my case?
>    - *EPS_ISO*: I've seen it mentioned a couple of times, but never if 
>    the value should be reduced or what to do with it exactly.
>    - *EPS_RHO0*: According to the reply of M. Krack 
>    <https://groups.google.com/g/cp2k/c/FUvjXq9RvWY/m/8VwHvHGUAgAJ> smaller 
>    values than the default give better accuracy.
>
> (FORCE_EVAL / DFT / MGRID)
>
>    - *CUTOFF*: This is generally lower than for a GPW calculation as I 
>    understand it but I guess I should perform a convergence test to choose an 
>    appropriate value. Alternatively, I could also multiply the relative cutoff 
>    by the maximum exponent in the soft basis set (PRINT_LEVEL MEDIUM to get 
>    the values right?) as you and Marcella suggested in another post 
>    <https://groups.google.com/g/cp2k/c/JX8bDi_w478/m/okVfMy6EAQAJ>.
>    - *REL_CUTOFF*: I'm a bit unsure about how to choose this as all the 
>    convergence schemes I've read about first converge the CUTOFF with a large 
>    REL_CUTOFF and then reduce the value of REL_CUTOFF to get the best balance 
>    between accuracy and efficiency, but as explained above, the rule of thumb 
>    for the cutoff uses the value of REL_CUTOFF to determine the CUTOFF...
>
> Any suggestions on how to optimize these parameters would be greatly 
> appreciated!
>
> I also have two other quick questions about your reply:
>
>    1. I thought that GPW was used for pseudopotential calculations and 
>    GAPW was used for all electron calculations, but now you say that you can 
>    also do pseudopotential calculations with GAPW. Is there an advantage to 
>    using GAPW over GPW? I know that the disadvantage is that some features are 
>    not present for GAPW calculations, but is there a reason to use GPW if all 
>    your intended features are implemented for GAPW?
>    2. The BASIS_MOLOPT_UZH file contains SVP,- TZVPP- and 
>    QZVPP-MOLOPT-GGA-ae basis sets. Is there also a double zeta all electron 
>    (MOLOPT) basis set somewhere I can use? I have always been told that single 
>    zetas are not intended for production runs, but I suspect that TZVPP is 
>    already quite computationally expensive for a pre-optimization.
>
> My apologies for the barrage of questions, but I don't have anyone in my 
> group with experience in CP2K so it's hard sometimes to figure these things 
> out on my own...
>
> Thanks in advance and for your previous reply!
>
> Kind regards,
> Léon
> On Tuesday, 14 November 2023 at 10:51:05 UTC+1 Jürg Hutter wrote:
>
>> Hi 
>>
>> For a pseudopotential calculation you can just change "METHOD GPW" to 
>> "METHOD GAPW". 
>> If you want to do all electron calculations, you also need to use 
>> corresponding 
>> basis sets and potentials, e.g. 
>> BASIS_SET SVP-MOLOPT-GGA-ae 
>> POTENTIAL ALL 
>> Use the default settings first, check the lines 
>> Total charge density (r-space): -0.0000000683 
>> Total Rho_soft + Rho0_soft (g-space): -0.0000000043 
>> in the output. If those values are larger than 0.00001 you need probably 
>> to 
>> change defaults. 
>> See the regtests and manual for more information. 
>> Come back here for if this basic setup fails. 
>>
>> regards 
>> JH 
>>
>> ________________________________________ 
>> From: cp... at googlegroups.com <cp... at googlegroups.com> on behalf of Léon 
>> Luntadila Lufungula <Leon.luntad... at uantwerpen.be> 
>> Sent: Wednesday, November 8, 2023 5:21 PM 
>> To: cp2k 
>> Subject: [CP2K:19481] Switching from GPW to GAPW 
>>
>> Dear all, 
>>
>> I want to perform an AIM analysis with Critic2 which (for as far as I 
>> know) requires an all-electron density (i.e. not the density obtained from 
>> a GPW calculation) and also plan to calculate NMR chemical shifts in the 
>> future which will also require the all-electron GAPW method. Currently, I 
>> have figured out how to do calculations with the GPW method but I'm still a 
>> bit unsure about how to go from a GPW to a GAPW calculation. Is there 
>> someone who could elaborate on what to look at when modifying my input 
>> file? I've looked into it a couple of times, but it's a lot of different 
>> parameters and I can't seem to figure out how it works... 
>>
>> All the best, 
>> Léon 
>>
>>
>> -- 
>> You received this message because you are subscribed to the Google Groups 
>> "cp2k" group. 
>> To unsubscribe from this group and stop receiving emails from it, send an 
>> email to cp2k+uns... at googlegroups.com<mailto:cp2k+uns... at googlegroups.com>. 
>>
>> To view this discussion on the web visit 
>> https://groups.google.com/d/msgid/cp2k/670d2377-8c38-4444-9130-14ebd3d32d09n%40googlegroups.com
>> <
>> https://groups.google.com/d/msgid/cp2k/670d2377-8c38-4444-9130-14ebd3d32d09n%40googlegroups.com?utm_medium=email&utm_source=footer>. 
>>
>>
>

-- 
You received this message because you are subscribed to the Google Groups "cp2k" group.
To unsubscribe from this group and stop receiving emails from it, send an email to cp2k+unsubscribe at googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/cp2k/c1df6a21-b2a2-4419-8393-340469d1651bn%40googlegroups.com.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.cp2k.org/archives/cp2k-user/attachments/20231116/e03639ae/attachment.htm>