Re: [h5md-user] Minor revisions before H5MD v1.0

[Felix Höfling]

Am 06.05.2013, 16:52 Uhr, schrieb Peter Colberg  
<address@hidden>:

> Hi Felix,
>
> On Mon, May 06, 2013 at 04:02:52PM +0200, Felix Höfling wrote:
> > It is not true that the interpretation of, e.g., the observable
> > "potential_energy" does not require the space dimension. It is for  
> > example
> > needed when analysing the fluctuations to compute the specific heat.  
> > (See
> > Allan & Tildesley, Chapter 2.5)
>
> Thank you for the clarification, I was ignorant of the physics.
>
> You refer to this formula, right?
>
> \langle\delta\mathscr{V}^2\rangle_{NVT} = k_B T^2 \left(C_V -  
> \frac{3}{2} N k_B\right)
>
> Peter

Yes, this is an example. The 3/2 reads actually d/2, this term is the  
ideal gas contribution and arises from kinetic energy fluctuations. I  
realised that one may compute the latter fluctuations as well, hoping that  
the value d/2 is reproduced.

Another example is eq. (2.84) in this book, where several observables  
enter and the system volume is needed. Hence, my suggestion is that such  
kind of analysis is only possible if /observables/box is present.

Cheers,

Felix