Benchmark all-electron ab initio quantum Monte Carlo calculations for small molecules

摘要

We study the efficiency, precision and accuracy of all-electron variationaland diffusion quantum Monte Carlo calculations using Slater basis sets.Starting from wave functions generated by Hartree-Fock and density functionaltheory, we describe an algorithm to enforce the electron-nucleus cusp conditionby linear projection. For the 55 molecules in the G2 set, the diffusion quantumMonte Carlo calculations recovers an average of 95% of the correlation energyand reproduces bond energies to a mean absolute deviation of 3.2 kcal/mol.Comparing the individual total energies with essentially exact values, weinvestigate the error cancellation in atomization and chemical reaction pathenergies, giving additional insight into the sizes of nodal surface errors.