title: Electron-nucleus cusp correction scheme for the relativistic zeroth-order regular approximation quantum Monte Carlo method.
abstract: A cusp correction scheme for the relativistic zeroth-order regular approximation (ZORA) quantum Monte Carlo method is proposed by extending the nonrelativistic cusp correction scheme of Ma et al. [J. Chem. Phys. 122, 224322 (2005)]. In this scheme, molecular orbitals that appear in Slater-Jastrow type wave functions are replaced with the exponential-type correction functions within a correction radius. Analysis of the behavior of the ZORA local energy in electron-nucleus collisions reveals that the Kato's cusp condition is not applicable to the ZORA QMC method. The divergence of the electron-nucleus Coulomb potential term in the ZORA local energy is remedied by adding a new logarithmic correction term. This method is shown to be useful for improving the numerical stability of the ZORA-QMC calculations using both Gaussian and Slater basis functions.
authors.affiliation: Department of Applied Chemistry, School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan. yutaka@qcl.t.u-tokyo.ac.jp
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Nakatsuka
authors.forename: Takahito
authors.initials: T
authors.lastname: Nakajima
authors.forename: Kimihiko
authors.initials: K
authors.lastname: Hirao