# CCL: Ewald Sum

*From*: Vincent Leroux <vincent.leroux###loria.fr>
*Subject*: CCL: Ewald Sum
*Date*: Tue, 25 Nov 2008 10:24:14 +0100

Sent to CCL by: Vincent Leroux [vincent.leroux,+,loria.fr]
Hi Leyla,

`You really should not try to understand Ewald sum method straight from
``source code, even if in this case it is well documented. The Ewald sum
``is done in Fourier space so first make sure you master this
mathematical
``concept.
` http://en.wikipedia.org/wiki/Fourier_transformation
http://en.wikipedia.org/wiki/Ewald_summation

`Then if you want, try to see how the conversion to Fourier space is
``handled in the code, how the summation is done, how code is optimized
so
``that terms that can be computed once and for all are grouped in the
``setup routine, etc. The routine here is particularly simple! Actual MD
``programs such as NAMD rely on the same principles but with a good
number
``of additional optimizations, in particular the code is heavily
``parallelized. This is much more complex, hopefully you do not need to
``master the code in order to understand and perform MD...
`

`For theoretical basis of molecular mechanics I strongly recommend you
``read A.R.Leach's book, if not done already.
` http://www.booksites.net/leach2/molecular/molecular_modelling_2.html
Good luck for your PhD ^^
VL
Leyla Ramin lram5228%%usyd.edu.au a écrit :

Sent to CCL by: "Leyla Ramin" [lram5228[A]usyd.edu.au]
I am PhD student in Sydney university and I am working in molecular dynamic
simulation, The codes in fortran language in your website in part:sources,
allen-tildesley-book "http://www.ccl.net/cca/software/SOURCES/FORTRAN/allen-tildesley-book/index.shtml>";
is so useful for me.

`In the "FICHE F.22. ROUTINES TO PERFORM THE EWALD SUM" the
routine is
``so complicated to understand the method. I am wondering if I can get
more information about this code.
` Please kindly advise me and thanks for your consideration.
Best Regards
Leyla Ramin