The nodes of Hartree-Fock wavefunctions and their orbitals

Hartree-Fock generated orbitals and wavefunctions feature nodes and nodal artefacts due to theory and different aspects of practical computation (basis set truncation and arrangement, as well as convergence limitations). We find that nodal artefacts occur even in high precision near complete basis set limit calculations. The beryllium atom is studied in detail. The consequences of our discussions have implications for Quantum Monte Carlo studies and the numerical investigation of fermion nodes.