From Holes to Functionals

What does this mean If we compare equation (6-9) which we just derived with its counterpart which can be deduced from equation (2-19) of Chapter 2 (by adding to the Eee term of the electron-electron interaction described in that expression the kinetic energy and the contribution from the external potential) 

As already alluded to above, the analysis of the properties of model hole functions that emerge from approximate exchange-correlation functionals is a major tool for assessing 

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