Quantum Monte Carlo simulation of spin-polarized tritium

The ground-state properties of spin-polarized tritium T$\downarrow$ at zero temperature are obtained by means of diffusion Monte Carlo calculations. Using an accurate {\em ab initio} T$\downarrow$-T$\downarrow$ interatomic potential we have studied its liquid phase, from the spinodal point until densities above its freezing point. The equilibrium density of the liquid is significantly higher and the equilibrium energy of $-3.664(6)$ K significantly lower than in previous approximate descriptions. The solid phase has also been studied for three lattices up to high pressures, and we find that hcp lattice is slightly preferred. The liquid-solid phase transition has been determined using the double-tangent Maxwell construction; at zero temperature, bulk tritium freezes at a pressure of $P=9(1)$ bar.Comment: 8 page

Quantum Monte Carlo study of large spin-polarized tritium clusters

This work expands recent investigations in the field of spin-polarized tritium T↓ clusters. We report the results for the ground-state energy and structural properties of large T↓ clusters consisting of up to 320 atoms. All calculations have been performed with variational and diffusion Monte Carlo methods, using an accurate ab initio interatomic potential. Our results for N 40 are in good agreement with results obtained by other groups. Using a liquid-drop expression for the energy per particle, we estimate the liquid equilibrium density, which is in good agreement with our recently obtained results for bulk T↓. In addition, the calculations of the energy for large clusters have allowed for an estimation of the surface tension. From the mean-square radius of the drop, determined using unbiased estimators, we determine the dependence of the radii on the size of the cluster and extract the unit radius of the T↓ liquid

Quantum Monte Carlo study of large spin-polarized tritium clusters

This work expands recent investigations in the field of spin-polarized tritium T↓ clusters. We report the results for the ground-state energy and structural properties of large T↓ clusters consisting of up to 320 atoms. All calculations have been performed with variational and diffusion Monte Carlo methods, using an accurate ab initio interatomic potential. Our results for N 40 are in good agreement with results obtained by other groups. Using a liquid-drop expression for the energy per particle, we estimate the liquid equilibrium density, which is in good agreement with our recently obtained results for bulk T↓. In addition, the calculations of the energy for large clusters have allowed for an estimation of the surface tension. From the mean-square radius of the drop, determined using unbiased estimators, we determine the dependence of the radii on the size of the cluster and extract the unit radius of the T↓ liquid

Quantum Monte Carlo simulation of spin-polarized tritium

The ground-state properties of spin-polarized tritium T↓ at zero temperature are obtained by means of diffusion Monte Carlo calculations. Using an accurate ab initio T↓-T↓ interatomic potential we have studied its liquid phase, from the spinodal point until densities above its freezing point. The equilibrium density of the liquid is significantly higher and the equilibrium energy of −3.664(6) K significantly lower than in previous approximate descriptions. The solid phase has also been studied for three lattices up to high pressures and we find that hcp lattice is slightly preferred. The liquid-solid phase transition has been determined using the double-tangent Maxwell construction; at zero temperature, bulk tritium freezes at a pressure of P=9(1) bar

Universality in molecular halo clusters

The ground state of weakly bound dimers and trimers with a radius extending well into the classically forbidden region is explored, with the goal to test the predicted universality of quantum halo states. The focus of the study is molecules consisting of T down arrow, D down arrow, He-3, He-4, and alkali atoms, where the interaction between particles is much better known than in the case of nuclei, which are traditional examples of quantum halos. The study of realistic systems is supplemented by model calculations in order to analyze how low-energy properties depend on the interaction potential. The use of variational and diffusion Monte Carlo methods enabled a very precise calculation of both the size and binding energy of the trimers. In the quantum halo regime, and for large values of scaled binding energies, all clusters follow almost the same universal line. As the scaled binding energy decreases, Borromean states separate from tango trimers

Ground state of small mixed helium and spin-polarized tritium clusters: A quantum Monte Carlo study

We report results for the ground-state energy and structural properties of small 4He–T↓ clusters consisting of up to four T↓ and eight 4He atoms. These results have been obtained using very well-known 4He–4He and T↓– T↓ interaction potentials and several models for the 4He– 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 4He– T↓ interatomic potential but the stability limits remain unchanged. The only exception is the 4He2T↓ trimer whose stability in the case of the weakest 4He– T↓ interaction potential is uncertain while it seems stable for other potentials. The mixed trimer 4He(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