A fixed-node Diffusion Monte Carlo study of the 1,2,3-tridehydrobenzene triradical

摘要

The electronic structure of 1,2,3-tridehydrobenzene was investigated using quantum Monte Carlo methods. The radical contains two low-lying electronic states that are nearly degenerate adiabatically (within 2 kcal/mol separation), according to previous coupled cluster calculations. We performed Diffusion Monte Carlo (DMC) calculations starting from Multi-Reference Configuration Interaction (MRCI) trial wavefunctions, with a complete active space (CAS) containing 9 electrons in 9 orbitals, CAS(9,9). Our converged DMC results are in close agreement with the best coupledcluster results, and further strengthen the assignment of a ~2A_1 ground state.