Colloid The colloid node allows to define a particle distribution. This node is only used in the Mie node.

Colloid are described with a dielectric function (Absorbance or Complex), the volumic density (or the percentage of volume occupied by particles) and the size density distribution.

The size density distribution is defined as $N(r)$ and correspond as the « Particle number density distribution », the size’s unit is micrometers and the value is just a number. Be careful of the type on your size distribution :

  • \(r^3 N(r)\) : Volume frequency \(\left [\mu m^{-1}\right]\)

  • \(N(r)\) : Particle Number density distribution \(\left [\mu m^{-3}.\mu m^{-1}\right]\)

  • \(N(r) \text{d}r\) : Number density \(\left [\mu m^{-3}\right]\)

Such as the volumic concentration is :

\[\nu = \frac{4 \pi}{3} \int^{r_{max}}_{r_{min}} r^3 N(r) \text{d}r\]

The Lorenz-Mie theory used with colloids is well-defined for sperical particles and size-distribution can be ajusted for other shapes. Usually, the particle size is within a few nanometers and less than one millimeter.

Be careful, the pre-calculation time can be significant for a large particle size, a large number of colloids or an over-sampled size distribution.

Children Nodes

Dielectric function Particle

The dielectric function of the particle







Volumic density of particle, no unit

size distribution


The tabulated distribution of particle size. The first column is the apparent-radius of the particle in micrometers and should be ordered. The second column is the particle number density and does not need to be normalized.

Ocean XML 6.1 example

<colloid name="Gold" density="5.18e-005">
     <param name="sizedistribution" type="list">
             <row size="0.0935" value="10.202"/>
             <row size="0.0985" value="24.4251"/>
             <row size="0.1035" value="35.6239"/>
             <row size="0.1085" value="21.3833"/>
             <row size="0.1135" value="8.13718"/>
     <dielectricfunc type="linked" name="Particle" target="ocean-metals:Au"/>