Diffusion Quantum Monte Carlo Calculations of Excited States of Silicon

摘要

The band structure of silicon is calculated at the Gamma, X, and L wavevectors using diffusion quantum Monte Carlo methods. Excited states are formedby promoting an electron from the valence band into the conduction band. Weobtain good agreement with experiment for states around the gap region anddemonstrate that the method works equally well for direct and indirectexcitations, and that one can calculate many excited states at each wavevector. This work establishes the fixed-node DMC approach as an accurate methodfor calculating the energies of low lying excitations in solids.