Fixed-node errors in real space quantum Monte Carlo at high densities: closed-shell atomic correlation energies

We consider non-relativistic electron correlation energies of heavy noble gas atoms including the superheavy element Og. The corresponding data enables us to quantify fixed-node errors in real space quantum Monte Carlo methods as a function of the atomic number Z. We confirm that single-reference trial function nodes lead to an overall trend of mild decrease in recovered correlation energy with the increasing Z. This agrees with our previous study that has shown increasing fixed-node biases with the increasing electron density. We also estimate the value of the linear term in the asymptotic expansion of the atomic correlation energy.