Abstract: A novel quantum Monte Carlo(QMC) differential approach was proposed, which can be used to directly compute the energy difference between two systems on the basis of accurate fixednode QMC algorithm, allowing the statistical error in the order of 10-5 hartree and the electroncorrelation energy over 90% for the computation results. By using a “rigid move” model and Jacobi transformation, a good positive correlation between energies of two configurations for a molecule was obtained, and thus the acquisition of accurate energy differences and molecules’ potential energy surfaces for two investigated systems is feasible.

Key words: Accurate fixed-node quantum Monte Carlo method, Differential approach, Correlation sampling, Potential energy surface