Quantum Monte Carlo study of small pure and mixed spin-polarized tritium clusters

We have investigated the stability limits of small spin-polarized clusters consisting of up to ten spin-polarized tritium T down arrow atoms and the mixtures of T down arrow with spin-polarized deuterium D down arrow and hydrogen H down arrow atoms. All of our calculations have been performed using the variational and diffusion Monte Carlo methods. For clusters with D down arrow atoms, the released node procedure is used in cases where the wave function has nodes. In addition to the energy, we have also calculated the structure of small clusters using unbiased estimators. Results obtained for pure T down arrow clusters are in good accordance with previous calculations, confirming that the trimer is the smallest spin-polarized tritium cluster. Our results show that mixed T down arrow-H down arrow clusters having up to ten atoms are unstable and that it takes at least three tritium atoms to bind one, two, or three D down arrow atoms. Among all the considered clusters, we have found no other Borromean states except the ground state of the T down arrow trimer. (C) 2008 American Institute of Physics.