Pseudopotential Calculations on Actinium and Thorium by Quantum Monte Carlo

Abstract: Pseudopotential calculations of the ground state energies of actinium and thorium neutral atoms and some of their corresponding cations by using variational Monte Carlo (VMC) and diffusion Monte Carlo (DMC) methods have been performed. The fluctuation of the local energy that has been obtained is found to be below 2 a.u. in all cases under study. We also study the dependence of DMC energy on the size of the time step for actinium. The available results are quite encouraging for these heavy atoms.