QUANTUM MONTE-CARLO INVESTIGATION OF EXCHANGE AND CORRELATION IN SILICON

Realistic many-body wave functions for diamond-structure silicon are c onstructed for different values of the Coulomb coupling constant. The coupling-constant-integrated pair correlation function, the exchange-c orrelation hole, and the exchange-correlation energy density are calcu lated and compared with those obtained from the local density and aver age density approximations. We draw conclusions about the reasons for the success of the local density approximation and suggest a method fo r testing the effectiveness of exchange-correlation functionals.