The VDM method can be improved by including correlations that are missed in an
Hartree-Fock type ansatz. This is usually done in form of a Jastrow factor f(**R**,**R**')
as shown in Eq. 3.79,

(263) |

(264) |

where is the separation of the pair of particles. The coefficients and depend on density , inverse temperature , and on the type of interacting particles. They are derive that the fulfill the cusp condition at any temperature. The coefficients for a pair of electrons is given by,

(265) | |||

(266) |

For an electron and an ion of charge , they read,

(267) | |||

(268) |