Wikipedia states:
Kinetic diameter is a measure applied to atoms and molecules that expresses the likelihood that a molecule in a gas will collide with another molecule. It is an indication of the size of the molecule as a target.
And the following equation is given:
$$d^2 = \frac{1}{πln}$$
where,
$d$ is the kinetic diameter,
$r$ is the kinetic radius, $r = d/2$,
$l$ is the mean free path, and
$n$ is the number density of particles.
To me, this implies that the kinetic diameter can be altered by changing the number density of particles. Therefore, a change in pressure, volume, or concentration should would effect the kinetic diameter.
However, kinetic diameters are often discussed as if they were constants. Indeed, Wikipedia even gives a table of kinetic diameters for some common molecules.
Another definition of the kinetic diameter would be useful.
How is the kinetic diameter related to molecular structure? Can it be quantified as the distance between a pair of atoms?
If someone could also suggest a computational program to calculate the kinetic diameter of a molecule, that would also be of use.
