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 method can be applied to calculate molecular energy more exactly. An expansion of the eigenvalue of the energy for a system has been derived. It is proved that the value of the energy calculated using the traditional fixed-node method is only the zeroth order approximation of the eigenvalue of the energy. But when using this novel method, in the case of only increasing less computing amounts ( < 1%), the first order approximation, the second order approximation, and so on can be obtained conveniently with the detailed equations and steps in the practical calculation to calculate the values of the zeroth, first and second approximation of the energies of 1 1A, state of CH2, 1A2(C4h, acet) state of C8 and the ground-states of H2, LiH, Li2, and H2O The results indicate that for these states it needs only the 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.