Spin Stability of Small Atomic Clusters

ARMEN N. KOCHARIAN, Gayanath Fernando, Kalum Palandage +1 more

Philippe Depondt, Franz, Mertens, G.

Ivana Bešlić

The ground-state of the helium and spin-polarized hydrogen quantum clusters is investigated in this work using Quantum Monte Carlo methods, as well as the spin-polarized tritium (T↓) liquid. For small mixed helium clusters consisting of up to eight helium atoms the ground-state energy and structure have been obtained. Stability of the 3He4 4He3 cluster, which was previously considered unstable, is predicted. It is confirmed that tritium trimer (T↓)3 is an example of Borromean state. For pure large spin-polarized tritium clusters consisting of up to 320 atoms the ground-state energy is obtained. Stability limits have been investigated for small mixed (T↓)n(D↓)m clusters, for m ≥ 2 i n + m ≤ 10. Especially, it has been shown that all clusters (T↓)ND↓ are stable for N ≥ 3. It is also shown that even 60 T↓ atoms are not enough to form stable cluster (T↓)60H↓. Equation of state, spinodal density, energy per particle at the equilibrium density, unit radius and surface tension of the T↓ liquid have been determined using results obtained in the simulations of liquid phase.

I. Bešlić, Leandra Vranješ Markić, Jordi Boronat

We have investigated the stability limits of small spin-polarized clusters consisting of up to ten spin-polarized tritium T downward arrow atoms and the mixtures of T downward arrow with spin-polarized deuterium D downward arrow and hydrogen H downward arrow atoms. All of our calculations have been performed using the variational and diffusion Monte Carlo methods. For clusters with D downward 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 downward 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 downward arrow-H downward 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 downward arrow atoms. Among all the considered clusters, we have found no other Borromean states except the ground state of the T downward arrow trimer.

Sudha Srinivas, E. Torikai

Petar Stipanović, Leandra Vranješ Markić, Jordi Boronat +1 more

We report results for the ground-state energy and structural properties of small (4)He-T↓ clusters consisting of up to four T↓ and eight (4)He atoms. These results have been obtained using very well-known (4)He-(4)He and T↓- T↓ interaction potentials and several models for the (4)He- T↓ interatomic potential. All the calculations have been performed with variational and diffusion Monte Carlo methods. It takes at least three atoms to form a mixed bound state. In particular, for small clusters the binding energies are significantly affected by the precise form of the (4)He- T↓ interatomic potential but the stability limits remain unchanged. The only exception is the (4)He(2)T↓ trimer whose stability in the case of the weakest (4)He- T↓ interaction potential is uncertain while it seems stable for other potentials. The mixed trimer (4)He(T↓)(2), a candidate for the Borromean state, is not bound. All other studied clusters are stable. Some of the weakest bound clusters can be classified as quantum halo as a consequence of having high probability of being in a classically forbidden region.