Relativistic quantum Monte Carlo method using zeroth-order regular approximation Hamiltonian.

We propose a new relativistic treatment in the quantum Monte Carlo (QMC) technique using the zeroth-order regular approximation (ZORA) Hamiltonian. The novel ZORA local energy is derived, and its availability is examined with some variational Monte Carlo calculations. We optimize the wave functions variationally and evaluate the relativistic and correlation effects simultaneously. It is shown that our ZORA-QMC method with Jastrow-Slater wave functions can recover not only relativistic effects but also almost the same amount of electron correlations as the nonrelativistic QMC method can by evaluating the ionization potentials of the first row atoms, Li-Ne.