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From: David A. Case <case.scripps.edu>

Date: Tue, 14 Sep 2004 12:20:49 -0700

On Tue, Sep 14, 2004, Oliver Hucke wrote:

*>
*

*> o Is it correct that, if atoms disappear, the backward direction can not
*

*> be simulated. I.e. the hysteresis between the forward and the backward
*

*> direction, as an error estimate, can not be computed?
*

*> How should one estimate the error then?
*

In principle, TI does not have any concept of "direction". Each of the

averages of <dV/Dlambda> can be simulated independent of the others.

If you wish, you could perform a series with lambda = (say) 0.1, 0.3, 0.5, 0.7

and 0.9 (starting each new value from the end-point of the previous value).

Then you could do an additional set with lambda = 0.9, 0.7, 0.5, 0.3 and 0.1.

This could be then divided roughly into a "forward" and a "backward"

direction.

But the better to way to estimate errors is to try to determine the

uncertainty in <dV/dlambda> at each lambda point, then propagate these error

estimates into a uncertainty in the final result.

*>
*

*> o What meaning do dV/dL values have for lambda=0 and lambda=1 ?
*

The same as they mean at all other values of lambda? I clearly don't

understand the question: there is nothing special about the endpoints in terms

of the "meaning" of this value.

*>
*

*> o Where in the source code can I find the paragraphs relevant for TI?
*

In thermo_int.f (it's not hidden all that much!)

....dac

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Received on Tue Sep 14 2004 - 20:53:00 PDT

Date: Tue, 14 Sep 2004 12:20:49 -0700

On Tue, Sep 14, 2004, Oliver Hucke wrote:

In principle, TI does not have any concept of "direction". Each of the

averages of <dV/Dlambda> can be simulated independent of the others.

If you wish, you could perform a series with lambda = (say) 0.1, 0.3, 0.5, 0.7

and 0.9 (starting each new value from the end-point of the previous value).

Then you could do an additional set with lambda = 0.9, 0.7, 0.5, 0.3 and 0.1.

This could be then divided roughly into a "forward" and a "backward"

direction.

But the better to way to estimate errors is to try to determine the

uncertainty in <dV/dlambda> at each lambda point, then propagate these error

estimates into a uncertainty in the final result.

The same as they mean at all other values of lambda? I clearly don't

understand the question: there is nothing special about the endpoints in terms

of the "meaning" of this value.

In thermo_int.f (it's not hidden all that much!)

....dac

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