The CASINO forum

Dear Nguyen, The error message means that the number of available orbitals is less than the the number of spin-up or spin-down electrons - which obviously isn't going to work. Perhaps you should show your Quantum Espresso input files and the CASINO input file on the forum, and someone familiar with ...

Dear Nguyen, I think your question 3 is simply about re-representing your Bloch orbitals in a blip basis? If so, you don't need to provide centres.dat. (Note that using a localised basis set, e.g., blips, is a separate issue from transforming your Bloch orbitals to a set of localised orbitals. As Ka...

Dear Katharina, Thanks very much for reporting the issue - I agree there is a memory problem. It seems to have been introduced in patch 1d6d14ae, in which the call to dmc_annihilate_configs at the end of dmc_main was bypassed for the equilibration stage of a DMC calculation. This means that the data...

Dear Katharina, Sorry to hear about the memory problems. a) CASINO allocates configurations when they are born and deallocates them when they die, so the memory requirements fluctuate in time. The details of memory management are handled by the compiler and we have to hope that it is sensible. Perha...

P.S. I think the most likely reason for the apparent disagreement in the DMC results with different Jastrows is the need for a better treatment of population-control errors in the no-Jastrow case. I suggest varying the target weight in inverse proportion to the time step.

Dear Fan et al., A few quick comments: * The all-electron DMC energies obtained with different Jastrow factors ought to agree so long as time step bias is controlled, population-control bias is controlled and the equilibration period is long enough. * The Bohr radius of oxygen is 1/8 a.u., suggestin...

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... that was why I mentioned the possibility of jumping out of a local minimum, which varmin_linjas, but not varmin, can do.

However, I think this is all a long elaboration on my original answer of, "I don't know"!

Thanks,

Neil.

Dear Katharina, The unreweighted variance is not the same as the variance. To obtain an unbiased estimate of the latter as a function of parameters, it is necessary to use reweighting (i.e., correlated sampling). To do "true" variance minimisation in CASINO, set vm_reweight to T. Hence the...

Dear Katharina, Thanks for your question. The short answer is, "I don't know", but here are a couple more thoughts. Unreweighted variance minimisation isn't the same as either energy minimisation or variance minimisation, and has its (self-consistent) minimum in a different place. Hence it...