Coordination analysis

This modifier performs two types of computations:

Element-wise RDFs

The Compute partial RDFs option lets the modifier compute separate radial distribution functions for all pair-wise combinations of particle types or elements. The computed partial RDFs will be normalized such that the summation of the partial RDFs, weighted by the product of the two corresponding elemental concentrations, yields the total RDF. For example, for a binary system with two particle species ɑ and β, the modifier computes a set of three partials functions gɑɑ, gɑβ and gββ, which add up to the total distribution as follows:

g(r) = cɑ2 gɑɑ(r) + 2 cɑcβ gɑβ(r) + cβ2 gββ(r)

Here, the cɑ and cβ denote the concentrations of the two species in the system and the factor 2 in the mixed term appears due to gɑβ(r) and gβɑ(r) being always identical.

Time-averaged RDF

In the current program version, the Coordination analysis modifier can only calculate the instantaneous RDF for the current simulation frame. To calculate an average RDF over all frames of a simulation trajectory, you can use OVITO's scripting capabilities and let the Coordination analysis calculate the RDF for each frame and then average the histogram data over all frames with a few lines of Python code. See the corresponding section of the scripting manual for an example.

See also

CoordinationAnalysisModifier (Python API)