[Pw_forum] what's the unit of charge density

[vega lew]

Dear all

I just ploted the 3D charge density using pp.x code.  And XCRYSDEN was used
for displaying the 3D isosurface of charge density. When I set the isovalue
for different number, such as 0.15 or less, I fould the overlap of electron
cloud is quite meanful for different systems of distinct catalysis
activities. I wonder what the unit of charge density? and whether the
absolute value of it could be directly comparable for different systems (
same number of atoms, same element, only different in geometry of the
model)? if I adjust the same isovalue (~0.15) for two systems, I found the
the electron cloud is overlapped at reacive site for more reactive system
and the electron cloud is separated for less reactive system. Could I say
the chemical bond is stronger in reactive system and that bond is
responsible for the activities?

By the way, is there a tutorial for population analysis? I wonder where I
could find the value of overap population for a pair of atoms.

thank you for reading, any hints will be deeply appreciated.

vega

-- 
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Vega Lew ( weijia liu)
PH.D Candidate in Chemical Engineering
State Key Laboratory of Materials-oriented Chemical Engineering
College of Chemistry and Chemical Engineering
Nanjing University of Technology, 210009, Nanjing, Jiangsu, China
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Email: vegalew at gmail.com
Office: Room A705, Technical Innovation Building, Xinmofan Road 5#, Nanjing,
Jiangsu, China
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