A novel method for fixed-node quantum Monte Carlo

In this paper, a novel method for fixed-node quantum Monte Carlo is given. By comparing this method with the traditional fixed-node one, this novel me thod can be applied to calculate molecular energy more exactly. An expansio n of the eigenvalue of the energy for a system has been derived. It is prov ed that the value of the energy calculated using the traditional fixed-node method is only the zeroth order approximation of the eigenvalue of the ene rgy. But when using this novel method, in the case of only increasing less computing amounts ( < 1%), the rust order approximation, the second order a pproximation, and so on can be obtained conveniently withr the detailed equ ations and steps in the practical calculation to calculate the values of th e zeroth, first and second approximation of the energies of 1 (1)A(1) state of CH2, (1)A(g) (C-4h, acet) state of C-8 and the ground-states of H-2, Li H, Li-2, and H2O The results indicate that for these states it needs only t he second order approximation to obtain over 97% of electronic correlation energy, which demonstrates that this novel method is very excellent in both the computing accuracy and the amount of calculation required.