QUANTUM MONTE-CARLO STUDY OF DENSITY-FUNCTIONAL THEORY FOR A SEMICONDUCTING WIRE

We use diffusion quantum Monte Carlo (DQMC) techniques to obtain accur ate estimates of the components of the Kohn-Sham effective potential o f density-functional theory for a model semiconductor, and the corresp onding components of the energy functional, by determining the local p otential which, when filled with noninteracting electrons, reproduces the DQMC electron density. The results are compared with the widely us ed local-density approximation. There is a large deviation in the exch ange-correlation potential, a slight deviation in the electron density , but a very small deviation in the total energy and its components. W e also use DQMC techniques to calculate the quasiparticle band gap, an d hence the discontinuity DELTA in the exchange-correlation potential on the addition of an electron.