Quantum Monte Carlo study of ground and first excited state of C, N, O, F, and Ne atoms using Slater‐Jastrow‐Backflow wave function

Abstract

All-electron fixed-node diffusion quantum Monte Carlo energies of the two lowestlying states of C, N, O, F, and Ne atoms are reported. The Slater-Jastrow form is used as the trial wave function. We will use single-and multideterminant wave functions as the Slater part. The single-determinant wave function has been computed by the Hartree-Fock method and the multideterminant wave functions have been computed by the complete active space self-consistent field, configuration interaction with single and double excitation, configuration interaction with single, double, triple, and quadruple excitation and second-order configuration interaction. For the groundand first excited states, the multideterminant wave functions have computed more than 99% of the correlation energy. Significant improvements have been achieved using the backflow transformations and up to 99.8% of the correlation energy has been recovered. A very good agreement with the experimental data has been obtained for the excitation energies. K E Y W O R D S backflow transformation, excited state, ground state of C, N, O an F atoms, quantum montecarlo, Slater-Jastrow

Bandgaps in free‐standing monolayer TiO2: Ab initio diffusion quantum Monte Carlo study

“…As a promising tool, the QMC technique has been used previously to study diverse properties of bulk transition-metal oxides [23,[26][27][28], nanocrystals [29,30], atoms [31], molecules [32][33][34], 2D materials [35,36], diamond [37], MgSiO 3 perovskite [38], boron-nitride [39], point defects [40][41][42], Al [43], and Si [42,44,45] in previous studies. To date, to the best of our knowledge, this method has not been systematically used to calculate the bandgap parameters for freestanding 2D transition-metal oxides.…”