*VCM calculations use a trial function
whose parameters
are determined from the minimisation
of the average energy or its variance:
*

*A typical trial function for an electronic system is the product between
the Slater determinants of one particle orbitals (OPO), obtained from a
DFT calculation, multiplied by a function that describes the
particle correlations.
*

(2) | ||

(3) |

(4) |

*Many studies have shown that VMC calculations recover up to
of the correlation energy but the remaining contributions
are hard to conquer because the results cannot be improved
systematically in the VMC framework. As a matter of fact the main use
of VMC calculations in CASINO is to generate the configuration set needed
for the Diffusion Monte Carlo calculation.
*