It's well known that 'quality' of trial/guiding wave function in DMC calculations greatly decrease variance of DMC energy and thus reduce the time required to achieve desired accuracy. Guiding wave function defines the branching term as the energy difference between true ground-state energy and the local energy of the guiding function. The better guiding wave function approximates true ground-state the less DMC energy variates.
In general, the JASTROW VMC optimized trial wave function is a suitable choice of guiding wave function in DMC. But since there are several ways to do JASTROW optimization which one gives the best result in terms of the DMC energy variance?
In the dissertation QUANTUM MONTE CARLO. CALCULATIONS OF. ELECTRONIC EXCITATIONS. By. Andrew James Williamson. Robinson College, Cambridge. CHAPTER 4. OPTIMISING TRIAL WAVEFUNCTIONS It was stated that
So it is better use variance optimization of JASTROW wave function?The quality of the trial/guiding wave function does not directly affect the final DMC estimate of the total energy of a given system (apart from the fixed node approximation). However, the intrinsic variance of VMC energy determines the variance of the estimate of the total energy at each step of the diffusion process. Therefore, as in the VMC technique, the number of DMC moves required to achieve a specific variance of the mean, decreases linearly with the intrinsic variance of VMC energy.