double excPZ(double rs) double excpPZ(double rs)Return values:
- exc: value of Perdew-Zunger form for
- excp: value of Perdew-Zunger form for
Input:
- rs: value of
As described in lecture, the literature specifies the
exchange-correlation energy per electron 
as a
function of the average distance between electrons 
. Perdew and
Zunger (Phys. Rev. B 23, 5048 (1981).) gave one of the
earlier, simplest forms for 
,
where Table 1 gives the values of the constant coefficients.
Table: Table of coefficients for Perdew-Zunger form (3) of the
local exchange correlation functional.
Write routines of the two above two prototypes which compute
and 
for the Perdew-Zunger form.
