Data type: numb
May appear in a looped list containing '_exptl_crystal_id'
Enumeration range: 0.0 -> infinity
The effective number of electrons in the crystal unit cell contributing to F(000). It may contain dispersion contributions, and is calculated as F(000) = [ (sum f~r~)^2^ + (sum f~i~)^2^ ]^1/2^ f~r~ = real part of the scattering factors at theta = 0 f~i~ = imaginary part of the scattering factors at theta = 0 the sum is taken over each atom in the unit cell