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Density Functional Theory and the Local Density Approximation

Density Functional Theory and the Local Density Approximation

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<strong>Density</strong> <strong>Functional</strong> <strong>Theory</strong>:<br />

The History<br />

Thomas-Fermi-Dirac Model (1929):<br />

First model where <strong>the</strong> energy is expressed in<br />

terms of <strong>the</strong> electron density<br />

E. Fermi, Nobel laureate 1938<br />

Kohn-Hohenberg-Sham (1964):<br />

Exact univoque relationship between ground<br />

state energy <strong>and</strong> electron density<br />

W. Kohn, Nobel laureate 1998<br />

E xc [n] - Properties<br />

E<br />

xc<br />

=<br />

s<br />

e!<br />

e<br />

!<br />

[ n]<br />

( T [ n]<br />

! T [ n])<br />

+ ( V [ n]<br />

V [ n])<br />

H<br />

– Does not depend on V ext (<strong>the</strong> specific system): it is a<br />

‘universal’ functional.<br />

– The exact dependence on n(r) is unknown<br />

E xc must be approximated in applications

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