Zero-timestep extrapolation

General discussion of the Cambridge quantum Monte Carlo code CASINO; how to install and setup; how to use it; what it does; applications.
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varelse
Posts: 44
Joined: Mon Jun 10, 2013 10:17 pm

Zero-timestep extrapolation

Post by varelse »

Is it possible to estimate the order in which the zero-timestep extrapolation increases accuracy? I want to check if I need to run next DMC calculations, or just use the result of a single run.
Dario_Alfe
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Location: University College, London
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Re: Zero-timestep extrapolation

Post by Dario_Alfe »

Extrapolations are always dangerous, as we do not know what is the functional form of the energy as function of time step.
varelse
Posts: 44
Joined: Mon Jun 10, 2013 10:17 pm

Re: Zero-timestep extrapolation

Post by varelse »

Well, it should be linear if the timestep is small enough.
Dario_Alfe
Posts: 10
Joined: Wed Jan 15, 2014 12:17 am
Location: University College, London
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Re: Zero-timestep extrapolation

Post by Dario_Alfe »

maybe, but you don't know how small is small enough. Often you find that it looks linear in some range, then you keep decreasing the time step and find that it departs from the linearity that you thought you were observing.
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