Re: Pressure Discrepancy

From: Morad Alawneh (
Date: Fri Apr 20 2007 - 10:56:07 CDT

*Dear Sterling,

I reported the SE = SD/sqrt(N), so to get 95% CI, we need to multiply
the SE by 2.96. By using 17 as the 95% CI, the 1 bar value for Pzz is
within the range, which is I think what you are looking for. Regarding
the autocorrelation function, see the attachment, it looks the same as
the one for the total pressure. It shows how fast the no correlation for
Pzz. Just to let you know I have printed out the data every 1 ps.

Within the statistical error Pzz is fine, but the total pressure is not,
even I set the pressure to be 1 atm, and that what makes me confused.
You said it is not necessary to expect the total pressure be the same as
the target value, will you explain that to me?
**Unless the target value meant to be for Pzz, then every thing make sense.*

Morad Alawneh
Sterling Paramore wrote:
> What did the decorrelation time for Pzz end up being in your system?
> And what confidence interval are you reporting the standard error at?
> Also, you shouldn't necessarily expect the average total pressure to
> hit 1 bar exactly (only the zz component) since you used constant area.
> -Sterling
> On Apr 19, 2007, at 3:05 PM, Morad Alawneh wrote:
>> *Dear all,
>> I have here new results to show the pressure problem:
>> <Pzz> (bar) = 10.93 (+/- 5.75 SE) (+/- 575.24 SD)
>> <P> (bar) = -33.18 (+/- 3.61 SE) (+/- 361.23 SD)
>> <V> (A^-3) = 119800.89 (+/- 4.73 SE) (+/- 473.10 SD)
>> The results show stable average values but away from the target
>> pressure, which I conclude something is not right about pressure and
>> any quantity related to pressure should not be trusted until this
>> problem be figured out.
>> *

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