Negative Values in E_DENSITY_CUBE Files

[Brian Day]

Thank you both for your help!

-Brian

On Friday, June 29, 2018 at 4:29:35 AM UTC-4, Vladimir Rybkin wrote:
>
> Dear Brian,
>
> the electron density is measured as inverse volume, in cube file it's 
> /Bohr^3. So, to get the integral over space one has to weight the voxels by 
> elementary volume. 
>
> Yours,
>
> Vladimir
>
> четверг, 28 июня 2018 г., 20:45:23 UTC+2 пользователь Brian Day написал:
>>
>> I'll have to try and play around with those parameters. That said, do you 
>> happen to know what the sum of the voxels in these files should be? I 
>> assume it should be (close to) 1 or (close to) the total number of 
>> electrons, but with the file attached above I get a value of 46. 34196, 
>> even though is only a two electron system. Thanks again.
>>
>> -Brian
>>
>> On Wednesday, June 27, 2018 at 3:49:47 PM UTC-4, Matt W wrote:
>>>
>>> 1e-14 seems a small number. I think you can put this down to numerics.
>>>
>>> Maybe decreasing EPS_DEFAULT in the QS section and the STRIDE keyword in 
>>> the E_DENSITY_CUBE section would give more accurate numbers.
>>>
>>> Matt
>>>
>>> On Wednesday, June 27, 2018 at 8:20:00 PM UTC+1, Brian Day wrote:
>>>>
>>>> I'm trying to generate .cube files of the electron density (probability 
>>>> density). I am using the following lines in my input files (also attached):
>>>>
>>>> &PRINT
>>>>    &MO_CUBES
>>>>       NHOMO -1
>>>>       NLUMO -1
>>>>    &END MO_CUBES
>>>>    &E_DENSITY_CUBE
>>>>    &END E_DENSITY_CUBE
>>>> &END PRINT
>>>>
>>>> I have noticed in the .cube file for the electron density (also 
>>>> attached), there are a number of values which are negative. Is this due to 
>>>> a numerical evaluation, or is there another reason for this that anyone is 
>>>> aware of? The negative values seem to range from -1e-18 to -1e-14, and the 
>>>> positive values seem to range from 1e-18 to 1e-9. Any help would be greatly 
>>>> appreciated!
>>>>
>>>> Thanks and Regards,
>>>>      Brian
>>>>
>>>>
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