The CASINO forum

Dear Shiv, Thanks very much for the new hist-plotting program! Some suggestions / advice for your suggested strategy (which looks fine): * For large systems, you may find that equilibration is more expensive than statistics accumulation. There are tricks for reducing this; e.g., if twist averaging y...

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One obvious point: a difference of 10,000 Hartree (=0.27 MeV) indicates that something has gone completely wrong in the calculations!

Best wishes,

Neil.

Dear Ichibha, The electron-nucleus cusp conditions are usually imposed by cusp-correcting the orbitals rather than via the Jastrow factor. By default the Gaussian cusp-correction scheme is applied to the orbitals (unless you have disabled it by setting cusp_correction=F). If you want to check that t...

Dear Vladimir,

Your postscriptum answers your question...

Best wishes,

Neil.

Dear Subhodip, VMC and DMC are zero-temperature methods that work in fixed simulation cells. If you want to calculate the equation of state of a solid then you need to calculate the DMC energy as a function of cell volume E(V). The static-lattice pressure at zero temperature can then be evaluated as...

Dear Dmitry, To my knowledge no results on Ps2, etc., have been published using exmol. It was implemented by Pablo and you might want to ask him about this... The H term is a polynomial three-body Jastrow term, a bit like the f term (which is a three-body term for two electrons and an ion). The cust...

Dear Ryan, The data written to local_energy.dat by CASINO is information relating to the cusp-correction scheme for Gaussian orbitals. It is a single-orbital "local energy": see J. Chem. Phys. 122 , 224322 (2005). It is not obviously related to the true local energy. I've never used VASP, ...

Dear Katharina, Yes, in principle making the trial wave function slightly worse will make time step, population-control and pseudopotential locality biases slightly worse. However, you are presumably planning to get rid of the former by extrapolating to zero time step. So long as you are sensible wi...

Dear Katharina, The varmin-linjas method scales as O(P^4), where P is the number of parameters (and the arrays get correspondingly large). I recently fixed an integer overflow that could occur in varmin-linjas with huge numbers of parameters. I would be cautious about using varmin-linjas for more th...