Abstract
Electronic energies are calculated for a Hubbard model on the molecule using projector quantum Monte Carlo (QMC) methods. The calculations are performed to an accuracy high enough to determine the pair-binding energy for two electrons added to neutral . The method itself is checked against a variety of other quantum Monte Carlo methods as well as the exact diagonalization for smaller molecules. The conclusion is that the ground state with two extra electrons on one molecule is a triplet, and, over the range of parameters where QMC is reliable, it has a slightly higher energy than the state with electrons on two separate molecules, so that the pair is unbound.
- Received 16 November 2004
DOI:https://doi.org/10.1103/PhysRevB.71.165436
©2005 American Physical Society