Role of Electron-Electron Coalescence Density in Density Functional Theory

摘要

An expression for the evaluation of electron-electron coalescence density as a functional of the density for any electron system is proposed. The formula, clarifies previously advanced upper bounds for this quantity and provides a method to independently estimate the system-averaged on-top exchange-correlation hole. The relationship with the on-top pair density shows that producing the true electron-electron coalescence should be considered as a leading physical requirement for trial wave functions in any energy minimization scheme.