Negative Values in E_DENSITY_CUBE Files

Vladimir Rybkin rybk... at
Fri Jun 29 08:29:35 UTC 2018

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. 



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
>>> 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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