[QE-users] Counting Basis Functions

[Stefano Baroni]

number of basis functions = number of plane waves in the wave-function expansion
SB

> On 19 Feb 2020, at 18:33, Ben Comer <bcomer3 at gatech.edu> wrote:
> 
> Thanks for this! I'm not familiar with how this translates into basis functions. How many total basis functions does this result in, and how would I calculate the number? is it just 499x199x55 = 5,461,555?
> 
> On 2/19/20 12:16 PM, Stefano de Gironcoli wrote:
>> On 19/02/20 17:58, Ben Comer wrote:
>>> sticks:   dense  smooth     PW G-vecs:    dense smooth      PW
>>>      Sum         499     199        55                     51837 13151      1677 
>> 
>> there are 51837 G vectors such that ekin < ecutrho   ... this is used to expand the density
>> 
>> there are 131151 G-vectorse such that ekin < ecutwfc*4 ... this is used to apply the potential on a wfc
>> 
>> there are  1677 G-vectrose such that ekin < ecutwfc ...  this used to expand the wfcs
>> 
>> -
>> 
>> sticks refers to the fact that G-vectors are organized in z-oriented sticks. this affects the fft distribution
>> 
>>  499 non empty sticks in the FFT up to ecutrho, 199 non empty sticks in the FFT up to ecutwfc*4, 55 non-empty sticks in the FFT up to Ecutwfc
>> 
>> 
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