Abstract
The dynamical exchange-correlation kernel of a nonuniform electron gas is an essential input for the time-dependent density-functional theory of electronic systems. The long-wavelength behavior of this kernel is known to be of the form where is the wave vector and is a frequency-dependent coefficient. We show that in the limit of weak nonuniformity the coefficient has a simple and exact expression in terms of the ground-state density and the frequency-dependent kernel of a uniform electron gas at the average density. We present an approximate evaluation of this expression for Si and discuss its implications for the theory of excitonic effects.
- Received 26 November 2008
DOI:https://doi.org/10.1103/PhysRevLett.102.113001
©2009 American Physical Society