Search found 113 matches
- Fri Nov 28, 2014 4:21 pm
- Forum: The CASINO program
- Topic: scaling of casino
- Replies: 4
- Views: 11303
Re: scaling of casino
Dear Katharina, The time should only depend weakly on the blip multiplicity. Usually the time spent evaluating blip orbitals is dominated by the time spent evaluating the blip functions themselves. (On the other hand, the memory requirements will increase rapidly with blip multiplicity.) The time ta...
- Mon Oct 06, 2014 9:56 pm
- Forum: The CASINO program
- Topic: Reblock convergence with large number of walkers
- Replies: 1
- Views: 8373
Re: Reblock convergence with large number of walkers
Dear Kayahan, For the DMC statistics accumulation stage, to achieve a given error bar you need to sample a given number of independent configurations. In principle the computational expense is the same, irrespective of whether you use a large population and a small number of steps or a small populat...
- Tue May 06, 2014 4:25 pm
- Forum: The CASINO program
- Topic: finite size corrections in 2D
- Replies: 6
- Views: 15873
Re: finite size corrections in 2D
Dear Dario, The relevant bit of code predates the finite-size paper by two years, suggesting that the finite-size correction to the exchange-correlation energy wasn't implemented in 2D because the expression for the correction wasn't known at the time. If you have accumulated the static structure fa...
- Tue May 06, 2014 3:53 pm
- Forum: The CASINO program
- Topic: finite size corrections in 2D
- Replies: 6
- Views: 15873
Re: finite size corrections in 2D
Dear Dario, Formulae for finite-size corrections in 2D - to both the interaction energy and the kinetic energy - can be found in N.D. Drummond et al. , Phys. Rev. B 78 , 125106 (2008). The leading-order correction to both the interaction energy and the kinetic energy is positive and scales as N ^(-1...
- Tue Mar 11, 2014 10:48 pm
- Forum: The CASINO program
- Topic: CASINO in a dielectric medium
- Replies: 1
- Views: 8791
Re: CASINO in a dielectric medium
Do you envisage calculations for a model system (pair of two-dimensional electron gases, with an effective interaction between the electrons)?
Modifying the form of the interaction between particles is straightforward, but would require a change to the code.
Best wishes,
Neil.
Modifying the form of the interaction between particles is straightforward, but would require a change to the code.
Best wishes,
Neil.
- Fri Nov 29, 2013 3:53 pm
- Forum: The CASINO program
- Topic: high vmc_ave_period and correlation less than 1
- Replies: 1
- Views: 8001
Re: high vmc_ave_period and correlation less than 1
Dear Varelse, If the correlation period is one step (it can't really be smaller) then you would expect the reblocked error bars to "start" in a plateau (i.e., you won't see the error bar rise with reblocking transformation before reaching the plateau). In principle it doesn't matter what b...
- Tue Nov 19, 2013 8:42 pm
- Forum: The CASINO program
- Topic: Rough estimate about speed of Casino
- Replies: 4
- Views: 14156
Re: Rough estimate about speed of Casino
Dear Amartya, If you are interested in an energy per atom then the CPU time for DMC statistics accumulation to achieve a given error bar is linear in the number of particles in the supercell. If you are interested in total energies, e.g., because you want to calculate points on a band structure, the...
- Tue Nov 19, 2013 5:46 pm
- Forum: The CASINO program
- Topic: Rough estimate about speed of Casino
- Replies: 4
- Views: 14156
Re: Rough estimate about speed of Casino
Dear Amartya, Depends on how exactly you perform your calculations. Let's assume you use a supercell containing about 400 electrons, a Slater-Jastrow wave function, a time step of 0.01 a.u. and 4 configurations per core, with 1000 cores, in your DMC calculations. You will probably need to carry out ...
- Fri Oct 25, 2013 9:31 pm
- Forum: The CASINO program
- Topic: Cutoff lengths in the Jastrow factor
- Replies: 12
- Views: 31506
Re: Cutoff lengths in the Jastrow factor
Dear Varelse, The cutoff length behaviour you describe seems a bit unusual; nevertheless every system is unique and, if the energy expectation value is going down, one cannot argue with the variational principle. If you are looking at similar systems then I would certainly make use of what you have ...
- Fri Sep 20, 2013 2:02 pm
- Forum: The CASINO program
- Topic: Jastrow optimisation, the default in 2.12
- Replies: 15
- Views: 37412
Re: Jastrow optimisation, the default in 2.12
Dear Philip,
I suggest using a 2x2x1 grid with inversion symmetry, which will allow a real wave function, for the optimisation of the Jastrow factor. You can then use that Jastrow factor for all offsets to your 2x2x1 grid of k vectors.
Best wishes,
Neil.
I suggest using a 2x2x1 grid with inversion symmetry, which will allow a real wave function, for the optimisation of the Jastrow factor. You can then use that Jastrow factor for all offsets to your 2x2x1 grid of k vectors.
Best wishes,
Neil.