Minimum principles and level splitting in quantum Monte Carlo excitation energies: Application to diamond
نویسندگان
چکیده
A diffusion and variational quantum Monte Carlo ~DMC and VMC! study of excitation energies in diamond is reported. Good agreement is found between the DMC results and results from the GW approximation and, where available, with experiment. A group theoretical analysis is provided of the level splittings arising from the use of arbitrary degenerate single-particle orbitals in the construction of groundand excited-state determinants. The results are discussed in light of the recently demonstrated variational theorems for excited states in the DMC study.
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