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Implementation of the new Jastrow Function

Another significant advantage of the optimisation procedure of Eq.(gif) is that new functions such as tex2html_wrap_inline7145 can be tested without actually having to implement them into the mainstream solid VMC code. All one has to be able to do is calculate tex2html_wrap_inline7263 and tex2html_wrap_inline5895 for each configuration. The optimisation of Eq.(gif) can then be performed to see if the proposed new function produces an improvement in the quality of tex2html_wrap_inline6049 , i.e. a reduction in the energy and variance of the energy. To calculate the new value for tex2html_wrap_inline5895 with tex2html_wrap_inline7145 included, the Jastrow factor in Eq.(gif) is written as


where the sum over pairs of electrons 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 was moved in the VMC calculation.

To calculate the new value of the kinetic energy with tex2html_wrap_inline7145 included in the wavefunction, the gradient and Laplacian of the new tex2html_wrap_inline7145 also need to be calculated. This was done in a similar way to Eq.(gif), by summing the contributions to the gradient and Laplacian of tex2html_wrap_inline7145 from each ion in the solid.

Andrew Williamson
Tue Nov 19 17:11:34 GMT 1996