The CASINO forum

Dear Philip / Mike, Varmin-linjas for complex wave functions is on my to-do list, although it's not likely to get done for a while. Note that optimisation for complex wave functions is rarely needed. When twist averaging, the same Jastrow factor is normally used at all twists. Hence one can perform ...

Dear Varelse,

It is unusual for the cutoff length of u to shrink like that, although certainly not impossible. Did the energy & variance decrease over successive optimisation cycles?

Best wishes,

Neil.

Dear Elaheh & Mike, I have occasionally encountered this problem on the Polaris cluster in Leeds. The problem is not reproducible (a job that fails can simply be resubmitted). I don't think it is a problem with CASINO; it is more likely to be a problem with the filesystem on Polaris. We could pe...

If the optimisation looked fine in other regards then I would simply continue the optimisation with more configurations.

Best wishes,

Neil.

Dear Varelse, Type "casinohelp jastrow_plot" to see the format of the JASTROW_PLOT block. Use e.g. %block jastrow_plot 1 1 2 0 0 0 1 0 0 2 0 0 %endblock jastrow_plot to plot u(r) for antiparallel-spin electrons, chi(r) for spin-up electrons and f with one electron at (0,0,0) and the other ...

Dear Mauro, It is evaluating numerical derivatives of the local energies with respect to wave-function parameters. If you are just optimising a Jastrow factor and you have fixed the cutoff lengths, you can use opt_method=varmin_linjas. This is an optimised variance minimisation algorithm for the lin...

Dear Mauro, Reusing the Jastrow u, chi and f terms should give a reasonable starting point. Note however that the cutoff length for u cannot exceed the Wigner-Seitz-cell radius. Hence if you are going from a larger simulation cell to a smaller cell you may need to reduce the cutoff length for u, in ...

Dear Jhalak, If you have eight unit cells in your simulation cell (2x2x2 primitive cells) and your primitive cell contains n electrons then the number of electrons in your simulation cell is N=8n . The number of primitive lattice points in the simulation cell must be eight. If you are relaxing the g...

P.S. The number of electrons in the simulation cell is simply given by the number of electrons in the primitive cell times the number of primitive cells in the simulation cell.

Dear Jhalak, Suppose we are interested in studying the bulk properties of a crystalline solid. We could in principle do this by looking at an enormous piece of the material surrounded by vacuum, but with current QMC technology we are limited to hundreds of atoms in our simulations. For this sort of ...