Quantum Monte Carlo simulation of spin-polarized tritium

TL;DR

This study uses diffusion Monte Carlo simulations to accurately determine the ground-state properties of spin-polarized tritium, revealing its phase behavior and phase transition details.

Contribution

First ab initio diffusion Monte Carlo study of spin-polarized tritium's liquid and solid phases with precise phase transition data.

Findings

Liquid equilibrium density is higher than previously estimated.

Equilibrium energy per particle is significantly lower at -3.664 K.

Solid phase favors hcp lattice and freezes at about 9 bar.

Abstract

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.