Difference between revisions of "Algorithms for Long Range Interactions"
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''' Long Range interactions page is under construction'''  ''' Long Range interactions page is under construction'''  
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+  == Publications ==  
+  <bibentry> deserno99b, wang01a, dejoannis02a, arnold02c, arnold02d, arnold02b, arnold05b, arnold05a</bibentry>  
== Useful references ==  == Useful references == 
Revision as of 23:02, 14 January 2008
Long Range interactions page is under construction
Contents
Long Range Interactions & the root of the problem
Formally a potential is defined to be short ranged if it decreases with distance quicker or similar than where is the dimensionality of the system. Electrostatic, gravitatory and dipolar interactions, present in many physical systems, are examples of long range interactions. When long range intgeractions are present in a system, the weight of the interactions comming from far particles is non negligible. Due to the type of decay with the distance of the interaction, as we go further an furhter the particleparticle interaction decreases but the number of interactions increases in such way that the contribution of the far particles to the total interaction of a particle can have a weight as large as the one due to the interaction of a particle with neighbour particles.
The limited power of current computers makes impossible simulate macroscopic bulky systems. We should always work with very small systems where the ratio area vs volume is large and therefore surface effects modify the behaviour respect to bulky systems. Furtheremore, due to the very small sizes accesible to us, the longrange component of the electrostatic interactions cannot be addresed in an exact manner.
Even if Moore´s law was able to hold on indefinitely, we would need still around two centuries to be able to tackle with systems of the size of about one cubic centimeter. Therefore, it is clear that we need to do some sort of approach in order to mimic bulky systems.
How to mimic bulky systems with long range interactions
The straight cutoff or subsequent shift of the longrange interactions in these systems have been observed to lead to many unphysical artifacts in the simulations. Better approaches currently available are:
 Reaction Field Methods.
 Periodic Boundary Conditions (artificial periodicity): LatticeSum Methods
 Hybrids of 2 and 3, eg. LSREF (Heinz2005).
 MEMD – Maxwell Equations Molecular Dynamics (*2)
Periodic Boundary Conditions
Frequently, periodic boundary conditions are used in simulations in order to approach bulk systems within the limits of currently available computers.
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Long Range interactions page is under construction
Publications

Wang, Zuowei and Holm, Christian.
"Estimate of the Cutoff Errors in the Ewald Summation for Dipolar Systems".
The Journal of Chemical Physics 115(6351), 2001.
[PDF] (2 MB) [DOI] 
Jason de Joannis and Axel Arnold and Christian Holm.
"Electrostatics in Periodic Slab Geometries II".
The Journal of Chemical Physics 117(2503–2512), 2002.
[PDF] (318 KB) [DOI] 
Arnold, Axel and de Joannis, Jason and Holm, Christian.
"Electrostatics in Periodic Slab Geometries I".
The Journal of Chemical Physics 117(2496–2502), 2002.
[PDF] (217 KB) [Preprint] [DOI] 
Arnold, Axel and de Joannis, Jason and Holm, Christian.
"Electrostatics in Periodic Slab Geometries II".
The Journal of Chemical Physics 117(2503–2512), 2002.
[PDF] (267 KB) [Preprint] [DOI] 
Axel Arnold and Christian Holm.
"A novel method for calculating electrostatic interactions in 2D periodic slab geometries".
Chemical Physics Letters 354(324–330), 2002.
[PDF] (425 KB) [DOI] 
Axel Arnold and Christian Holm.
"MMM1D: A method for calculating electrostatic interactions in 1D periodic geometries".
The Journal of Chemical Physics 123(12)(144103), 2005.
[PDF] (122 KB) [DOI] 
Axel Arnold and Christian Holm.
"Efficient methods to compute long range interactions for soft matter systems".
In Advanced Computer Simulation Approaches for Soft Matter Sciences II, volume II of Advances in Polymer Sciences, pages 59–109. Editors: C. Holm and K. Kremer,
Springer, Berlin, 2005.
[PDF] (2 MB) [DOI]
Useful references
[Heinz2005] Heinz et al , JCP 123, 034107, (2005). [*2] RottlerMaggs and DunwegPasichnyk,2004