[CP2K-user] [CP2K:17096] Re: Generating BQB formatted cube files through CP2K

[Sam Broderick]

So there are two strides that I have encountered in CP2K, which is 
confusing.

Stride in &REFTRAJ: STRIDE 8 indicates to take *TIME STEPS* 1, 9, 17, etc.

Stride in &E_DENSITY_CUBE: STRIDE 1 1 1 indicates to skip no *MESH 
locations*, but 2 2 2 would take every 2nd in x, y, z.

There is no need for the .cube if you output .bqb, but you will need either 
TRAVIS or bqbtool to read it.

On Wednesday, June 8, 2022 at 7:17:28 AM UTC+2 mhvg... at gmail.com wrote:

> Hi Sam,
>
> I'm not quite sure if I understand...
>
> I understood the stride to be more like the 'resolution' of the electron 
> density. That being said, I'm totally unfamiliar with AIMD, so I'm sure you 
> know better than me.
>
> I suppose what I'm asking is if it's possible to generate a .bqb file 
> *without* having to generate a full .cube file (because the .cube file is 
> prohibitively large)... or, is it possible for each frame of the .cube file 
> to be compressed into a .bqb file and then get discarded? Again, my main 
> concern is the memory requirements...
>
> Thanks for your help!
>
> Matthew
> On Tuesday, June 7, 2022 at 10:39:38 PM UTC+8 wave... at gmail.com wrote:
>
>> Hi Matthew
>>
>> So if you use the TRAVIS program, you can skip Voronoi in cp2k. TRAVIS 
>> will do this for you (it wasn't clear to me either reading the tutorial).
>>
>> The stride is not to be confused with &REFTRAJ stride for 
>> &E_DENSITY_CUBE. This is a sort of down-sampling to reduce file size. Since 
>> bqb is is design to compress, there's no need for a stride. This should be 
>> all you need.
>>
>> &E_DENSITY_BQB
>>     FILENAME =result-E0.bqb
>> &END E_DENSITY_BQB
>>
>> TRAVIS reads the bqb natively.
>>
>> Hope this helps
>> Sam
>> On Monday, June 6, 2022 at 1:55:48 PM UTC+2 mhvg... at gmail.com wrote:
>>
>>> Hi there,
>>>
>>> I'm following the IR spec tutorial in order to generate an IR spectrum 
>>> of my system. As far as I am aware, the BQB compression system has been 
>>> added to CP2K, but I can't figure out how to generate my electron density 
>>> into this compressed style of file.
>>>
>>> The tutorial mentions says that, to print the electron densities, you 
>>> need to include:
>>> &PRINT
>>>    &E_DENSITY_CUBE
>>>        STRIDE 1 1 1
>>> etc..
>>>
>>> In the documentation for the E_DENSITY_BQB, it doesn't list any 'STRIDE' 
>>> option (or equivalent), so it doesn't sound like it replaces the 
>>> E_DENSITY_CUBE command... Is it possible to generate BQB electron density 
>>> files in CP2K? If so, how can this be done?
>>>
>>> Also, the tutorial mentions that we are using the Voronoi integration, 
>>> and there is a VORONOI block in the DFT/PRINT block, but the tutorial never 
>>> mentions it... Is that related, at all?
>>>
>>> Thanks!
>>>
>>> Matthew~
>>>
>>

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