Dear Acoot:

The idea of convergence is this: start a large number of simulations from different conformations, analyze some quantity over time in each simulation, and when the deviation of the average value of that quantity from each separate simulation is less than the time-variance within individual simulations, then you can imply that the simulations have converged -- that is, the results of independent simulations which started as different are now similar.

There is a huge body of work that uses a single simulations and evaluates its so-called convergence using some assumptions and special methods. That can also be very useful, but I find it informative to think of "convergence" in its standard non-scientific dictionary definition as the coming together of previously disparate things.

For simulations, my working definition is this: a set of simulations has converged the value of some variable when the simulations were initiated from sufficiently distinct conformational basins and then, over time, the ensemble distribution of the time-averages of the specified variable has a variance that is the same as the mean time-averaged variation within independent simulations. The weak point here is the part about "sufficiently distinct conformations", but I am not sure that this can be stated less vaguely in the general case.

Chris.

-- original message --

Hi Justin,

Can you give me your definition of converged MD and unconverged MD?

Cheers,

Acoot


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