Quantum Monte Carlo study of water molecule: A preliminary investigation

The Quantum Monte Carlo (QMC) technique([1]) offers advantages of good scaling with system size ( number of electrons) and an ability to uniformly recover over 90% of the electron correlation energy, compared to the more conventional quantum chemistry approaches. For the water molecule in its ground state, it has been shown([2]) that the QMC method gives results that are comparable in accuracy to those obtained by the best available conventional methods, while at the same time using much more modest basis sets than is necessary with these methods. Furthermore, the effect of the orbitals needed for these QMC calculations (which may be obtained from either Hartree - Fock or Density Functional Theory) has been investigated. Both the advantages and disadvantages of the QMC method are discussed.