We give the first mathematically rigorous justification of the local density
approximation in density functional theory. We provide a quantitative estimate on
the difference between the grand-canonical Levy–Lieb energy of a given density (the
lowest possible energy of all quantum states having this density) and the
integral over the uniform electron gas energy of this density. The error involves
gradient terms and justifies the use of the local density approximation in
the situation where the density is very flat on sufficiently large regions in
space.
Keywords
Schrödinger operators, statistical mechanics, density
functional theory, uniform electron gas