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$\downarrow$ atoms and the mixtures of T$\downarrow$ with spin-polarized deuterium D$\downarrow$ and hydrogen H$\downarrow$ atoms. All of our calculations have been performed using the variational and diffusion Monte Carlo methods. For clusters with D$\downarrow$ 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$\downarrow$ 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$\downarrow$-H$\downarrow$ clusters having up to ten atoms are unstable and that it takes at least three tritium atoms to bind one, two or three D$\downarrow$ atoms. Among all the considered clusters, we have found no other Borromean states except the ground state of the T$\downarrow$ trimer.