Another significant advantage of the optimisation procedure
(
) is that new functions such as can be experimented
with without actually having to implement them into the mainstream
VMC code. All one has to be able to do is calculate 
and
for each configuration. The optimisation () can then
be performed to see if the new function produces the desired effect.
To calculate the new value for 
with included
the Jastrow factor in Eqn.() is written as
where the sum over pairs of electrons within L of each ion is performed by storing lists of which electrons are within L of each ion. The intention was to then update these lists whenever an electron moved in the VMC calculation. However, this is not necessary at this stage.
To calculate the new value for 
with included the
gradient and Laplacian of the new also need to be calculated.
This was done in a similar way to (), by summing the
gradients and Laplacian of about each ion in the solid.
