Dependence of quantum Monte Carlo fixed-node errors on electron density: electron correlation energies of closed-shell noble gas atoms up to Og

We consider non-relativistic electron correlation energies of heavy noble gas atoms including the superheavy element Og (atomic number Z=118). By combining previous calculations by several groups with our data and analysis we were able to estimate the values of correlation energies as well as to quantify fixed-node errors in real space quantum Monte Carlo (QMC) methods as a function of the atomic number Z. We confirm that single-reference trial function nodes exhibit an overall trend of mild decrease in recovered percentage of the QMC correlation energy with the increasing Z. This agrees with our previous study that has shown increasing fixed-node biases with the increasing electronic density. We also estimate the value of the linear term in the asymptotic expansion of the atomic correlation energy as a function of Z.