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3.2 Square Gradient Approximation (SGA)
A first improvement on the simple LDA is based on a gradient expansion
for
:
|
(3.3) |
Comparing this with the functional Taylor expansion of
we find
|
(3.4) |
The variational rule leads to
|
(3.5) |
Franz J. Vesely Oct 2001
See also: "Computational Physics - An Introduction," Kluwer-Plenum 2001